Image source, Getty Images

As Washington poured in billions of dollars to fight the Taliban insurgency and fund reconstruction after invading in 2001, troop numbers went up.

Other countries were also part of the foreign military presence, but the US had by far the biggest single contingent - and racked up the largest bill.

Between 2010-12, when the US had more than 100,000 soldiers in Afghanistan, the cost of the war had reached almost $100bn a year, going by official figures.

One academic study, which looked at war costs in both Afghanistan and Pakistan, estimated the US had spent around $978bn since the 2001 (this includes money allocated for 2020).

The UK and Germany - which had the largest numbers of troops after the US - spent an estimated $30bn and $19bn respectively.

Read more here.

The head of Afghan news service Tolo News, Lotfullah Najafizada, has tweeted this image of a man covering up pictures of women painted on a wall in Kabul.

Young women in the city have been pleading for help in recent days as the Taliban advanced towards Kabul.

Prior to 2002 when the Taliban controlled Afghanistan, the militants practiced a version of Sharia law which included stoning for adultery, amputation of limbs for theft, and preventing girls from going to school beyond the age of 12.

A Taliban official has just been quoted as saying that the decision on whether to impose punishments like this would be "up to the courts".

Reports from areas the Taliban have captured in recent days indicate that women are already not being allowed out of their homes without a male companion and that some female employees were told their jobs would now be carried out by men. Women in these areas are also being told to wear burkas.

Image source, European Photopress Agency

The BBC understands that UK parliament will sit on Wednesday, after a Downing Street source said Prime Minister Boris Johnson is set to recall MPs from the summer recess to discuss the situation in Afghanistan.

Shadow Foreign Secretary Lisa Nandy said: "It beggars belief that in the face of all that, the [UK] government has been so slow to respond.

"What we need to hear now is an actual strategy from the government."

She said it had been "clear for days" there had been a "catastrophic miscalculation" by the US and UK, who overestimated the strength of Afghanistan's government.

The decision by allies to pull out of Afghanistan showed a lack of "strategic patience", stripped the Afghan army of their logistics and air support and "convinced them there was no tomorrow", Conservative MP Tom Tugendhat told the BBC.

He suggested the strategy emboldened Taliban militants, allowing them to sweep through many major cities.

Mr Tugendhat, who is chairman of the Foreign Affairs Committee, said the UK had "abandoned the Afghan people".

Image source, AFP

People in Kabul have been fleeing the capital as news of the Taliban advance emerges.

Long queues of cars have formed as people try to find a way out of the city. Banks have also been busy as residents try to withdraw their savings.

Afghan MP Farzana Kochai, whom we were speaking to earlier, describes the scene: "I'm in my house and looking at the people who are just trying to run."

She continues:"I don't know where they're trying to go, even in the streets and from their houses, their bags they are carrying... and all these things. It's heartbreaking, you know."

Earlier, Pakistan said it was closing the Torkham border crossing with Afghanistan after the militants seized the Afghan side of the border, according to reports.

This leaves Kabul International Airport as the only way out of the country.

"Some people have left their keys in the car and have started walking to the airport," one resident told Reuters.

Taking UK and US support out of Afghanistan was "grossly and unbelievable irresponsible", the former UK international development secretary has told the BBC.

The UK and the US have been providing air support to Afghan forces fighting the Taliban - now that line of defence is being removed.

Those aircraft were "a keystone" to their defence and removing them meant "nothing could be held together", Rory Stewart said.

"It's very difficult for an army like the Afghan army to fight without any air support," he said.

"What President Biden, Mr Johnson and others have done just a few weeks ago is very cruelly removed, just a few weeks ago now, the vital thing that held the country together, and by doing so have allowed the Taliban to capture almost the entire country in a couple of days.

"I'm afraid it's too late now," he says. "They could take over in a few hours now so we are going to have to adjust to a horrifying situation in which a regime which brutalised women, provided safe haven to Osama Bin Laden, has a very aggressive attitude towards the West will be taking over country which for the last 20 years had had extraordinary opportunities to develop."

He says he is thinking of the millions of Afghan people whose lives had been transformed in the last 20 years but who are now "very, very frightened".

The Taliban has said that it has encircled Kabul, in one of its first public statements since news that its fighters were entering the city.

Taliban fighters began entering the city on Sunday after taking control of all of Afghanistan's major cities, apart from the capital, in just 10 days.

A Taliban official said that fighters would not be allowed to conduct celebratory gunfire. He added that members of the Afghan forces would be permitted to return to their homes.

The official was also quoted as saying that the airport and hospitals would be allowed to continue operating and that emergency supplies would not be blocked.

Foreigners have been told they can leave if they wish, or register their presence with Taliban administrators.

The US has stepped up evacuations of its embassy staff members with 5,000 troops on hand to help.

Many Afghans have been fleeing the Taliban advance and seeking refuge in the capital, Kabul. They have been staying in makeshift camps.

Image source, EPA

Image source, EPA

Image source, EPA

Image source, EPA

Image source, PA Media

We've heard in the last few minutes that the UK prime minister is expected to recall parliament for urgent talks over the situation in Afghanistan.

A statement by the leader of the opposition said MPs need to abandon the summer recess and return to the House of Commons to address government plans on how to avoid a humanitarian disaster in the region.

"The situation in Afghanistan is deeply shocking and seems to be worsening by the hour," said Sir Keir Starmer.

"The immediate priority now must be to get all British personnel and support staff safely out of Kabul.

"The government has been silent while Afghanistan collapses, which - let's be clear - will have ramifications for us here in the UK.

"We need parliament recalled so the government can update MPs on how it plans to work with allies to avoid a humanitarian crisis and a return to the days of Afghanistan being a base for extremists, whose purpose will be to threaten our interests, values and national security."

Taliban militants have taken control of all major Afghan cities except Kabul after a rapid advance through the country.

We look back at how they did it so fast.

• April: US President Joe Biden announces US troops will pull out of Afghanistan starting in May and ending on 11 September, bringing America's longest war to a close
• May: The Taliban launch a major offensive on Afghan forces in southern Helmand province, and attack in other provinces
• June: The UN envoy to Afghanistan says the Taliban have taken more than 50 of 370 districts. The Taliban launch a series of attacks in the north, far from their traditional strongholds in the south
• 21 July: The Taliban control about half of the country's districts, according to a senior US general, external
• 6 August: The militants capture Zaranj in the south, the first provincial capital to fall to them in a year

• 13 August: Four more provincial capitals fall in a day, including Kandahar, the country's second city

• 14 August: The Taliban take the major northern city of Mazar-i-Sharif
• 15 August: They capture the key eastern city of Jalalabad without a fight, closing in on Kabul

A BBC reporter in Kabul has been describing the mood in the city.

Many shops and markets are closed, and some people are saying they have "never been so worried".

Some government offices are also closed with the army and police leaving their duty posts in places.

Small bursts of gunfire have been heard in some areas, but the source is unclear.

Rumours have swirled online that Taliban militants breached Kabul. However, a Taliban spokesman says fighters have been told to stay at the city gates and not attack.

The chairman of the UK parliamentary foreign affairs committee has criticised Foreign Secretary Dominic Raab for remaining silent on the Taliban advance in Afghanistan.

Conservative MP Tom Tugendhat told the BBC: "This is clearly the biggest single disaster of British foreign policy since Suez [in 1956] and we're yet to hear a single word from the foreign secretary in the last week so I'm afraid I don't know what he thinks."

He says: "It is pretty extraordinary that our focus has been on minor negotiations with Nato and European partners and allies who we've worked with and traded with very, very closely for the last 70, 80, 90 years - rather than on the lives on 28 million Afghans, several thousands of whom have genuinely risked their lives in order to save the lives of British soldiers or to serve the interests of the British people in preventing terrorism keeping our country safe."

The BBC has contacted the Foreign Office asking for an interview but no one has been made available.

The Taliban say they have taken over Bagram airfield and prison, on the outskirts of Kabul.

The complex was the epicentre of the war against the Taliban and al-Qaeda for some 20 years until last month, when the US military left in the dead of night without notifying the Afghans.

The US-led coalition forces moved in during December 2001, and Bagram was developed into a huge base capable of holding up to 10,000 troops.

George W Bush, Barack Obama and Donald Trump all visited the base during their tenures as president.

Bagram also contains a prison, with a reported 5,000 Taliban inmates left in the facility. Taliban sources have claimed that they have released these prisoners.

Bagram prison famously became known as Afghanistan's Guantanamo - after the infamous US military prison in Cuba.

It was originally built and run by the Americans but was handed over to Afghan control in 2013.

Image source, Getty Images

UK Prime Minister Boris Johnson will call MPs back to the House of Commons next week for urgent talks over the situation in Afghanistan, a No 10 source has told the BBC.

The day and time will be confirmed with the Speaker of the house, it says.

Ethirajan Anbarasan
Anbarasan Ethirajan, BBC World Service

Image source, EPA

Panic and fear gripped Kabul after reports of Taliban fighters had been seen on the outskirts of the capital. A colleague told me some government offices were asked to evacuate and shops were closed. No reason was given.

By capturing neighbouring districts of the city, the Taliban are poised to target Kabul, the only major city under government control.

It is possible that many of their fighters could have infiltrated or be living inside Kabul as well. They hold all the military cards at the moment and are in a commanding position.

Any fighting over Kabul will result in huge civilian casualties and it’s going to be bloody. The Taliban are aware of that and they want to send a message to the international community that the new Taliban 2.0 are different from their earlier incarnation.

They have given safe passage to most surrendered soldiers and government officials in other provinces. Their psychological war against the security forces has worked so far - several provinces have been handed over without a fight.

They may play the same game in Kabul as well, as Western nations evacuate their nationals. They need international recognition and aid too.

The Taliban have already claimed that the withdrawal of American troops shows that they have defeated the world’s biggest military power.

It won’t be surprising if some of their local leaders think it will be a big propaganda victory if they can supervise the American and British evacuation too in the coming days.

The Taliban are close to retaking full control of Afghanistan, almost 20 years after being ousted by a US-led military coalition.

Emboldened by the withdrawal of US troops, they now control all key cities and are closing in on the capital, Kabul.

The BBC's Visual Journalism Team has been tracking their advance across the country.

People have been fleeing the Afghan capital city Kabul in their cars, causing long queues of standing traffic.

The Taliban are reportedly at the city gates but have ordered their fighters to refrain from perpetrating violence and to allow safe passage to anyone who chooses to leave.

Reuters news agency earlier reported that some people were abandoning their vehicles and even walking to the airport.

The situation in Kabul continues to move fast with fluid reporting.

The acting Afghan interior minister has appeared in a video, broadcast on local outlet Tolo TV, saying there would be a "peaceful transfer of power" to a transitional government. He said Kabul would not come under attack.

The Associated Press news agency, citing an Afghan official, said Taliban negotiators were heading to the presidential palace to prepare for a "transfer" of power.

The Taliban earlier said they had instructed fighters to wait at the city's gates.

According to a number of reports, the Taliban are said to have reconquered Bamiyan, where they infamously blew up two giant Buddhas some 20 years ago.

Three Afghan officials have told the Associated Press news agency that the Taliban were in the districts of Kalakan, Qarabagh and Paghman in the capital, Kabul.

Nili, the capital of the central province of Daykundi, has also surrendered to the Taliban without much resistance, reports say.

Britain is working to protect its citizens and help other eligible former UK staff to leave Afghanistan, the Home Office said as Taliban insurgents reached Kabul.

"Home Office officials are right now working to protect British nationals and help former UK staff and other eligible people travel to the UK," it said on Twitter., external

"The Home Office has already resettled over 3,300 Afghan staff and their families who have worked for the UK. We will continue to fulfil our international obligations and moral commitments," it added.

Image source, NAIMATULLAH ZAFARY

An Afghan man who was told he must defer his scholarship to study in the UK says students are begging for their places on the courses this year.

The Foreign Office said the disruption caused by the conflict meant the British embassy in Kabul could not issue visas for the Chevening Scholarships.

Naimatullah Zafary, 35, applied four years running before finally getting accepted to study governance, development and public policy at the University of Sussex.

At a meeting in the British embassy in Kabul, the students were "yelling, they were begging, 'please, please, allow us the visa'". Some were crying and some had panic attacks, he says.

Mr Zafary says it is hard for the students to accept the decision, when visas are still being issued to diplomatic staff and Afghans being relocated to the UK.

"When they said it will be paused for the next year, I don't believe it. If you cannot make it this year, how can you make it next year?" Mr Zafary says. "Every day, every second in this country is unpredictable."

More than 30 of the 35 students with places this year have resigned from their jobs in Afghanistan and some declined promotions.

Many of the women fear that as the Taliban extend their rule, their educational opportunities will disappear, Mr Zafary says.

There is also a risk that Chevening students will become targets, he adds.

Read more: UK scholarships for Afghan students paused