Jens Stoltenberg, Secretary General of Nato, has reacted to events unfolding at Kabul airport.

The Ministry of Defence said in a tweet: "There have been no reported UK military or UK Government casualties following the incidents in Kabul.

"UK forces are working closely with our partners to provide security and medical assistance."

Frank Gardner
BBC Security Correspondent

This was a combination of gunfire and explosives, which is a classic insurgent tactic.

It's what's been used in many of the urban attacks that have taken place in Afghanistan in recent months and years - usually with a suicide bomber setting off an explosion.

That's exactly what the intelligence services were warning was going to happen.

Deborah Haynes, foreign affairs editor with Sky News, has spoken with a former interpreter for UK forces who was waiting for an evacuation flight with his wife and young children when the explosions happened.

“It was like doomsday, injured people everywhere," he told her, adding that he "saw people running with blood on their faces and bodies".

Image source, EPA

An eyewitness to the attack outside Kabul airport has told a reporter at the scene that the blast was "really powerful".

"Where we were, there was suddenly an explosion," the man said in footage shared by Reuters.

He said he saw "at least 400 to 500 people" in the immediate area and described some of the victims as "foreign forces".

"We carried the wounded here on stretchers and... my clothes are completely bloodied," he said.

Barbara Plett Usher
BBC News, Washington

The US president is in the Situation Room along with the chairman of the Joint Chiefs of Staff and they are monitoring the information coming in, in terms of the security situation, the details of the explosion, the details of the casualties. US media have been reporting that a number of US personnel have been injured.

The president last week had started publicly warning about the threat of an attack, which he said might come from IS-K, the Afghanistan branch of the Islamic State group - and that is one of the main reasons we understand why he didn't want to extend the deadline of the evacuation.

• At least two explosions have been reported near the Abbey Gate, being used for evacuations at Kabul airport. One blast was near the Baron Hotel, being used as a staging post by Western nations for evacuations
• A Pentagon spokesman confirmed there had been a "number of US and civilian casualties" in the attack. There are pictures of bodies at the scene

• US officials also say there were reports of gunfire
• The bombings come hours after US and UK officials told their citizens to avoid the airport, citing an imminent threat from militants
• US President Joe Biden has been briefed and is monitoring the situation, with UK PM Boris Johnson set to chair an emergency response meeting later

Tom Tugendhat, UK Conservative MP and chairman of the Foreign Affairs Committee, says the attack highlights the chaos unleashed by Taliban rule:

Alicia Kearns, a member of the foreign affairs and national security strategy committees, said there had been "many hurt" in an attack near the Baron Hotel, where the UK is processing Britons and Afghans eligible for evacuation.

The Conservative MP tweeted: "A bomb or attack with gunfire at northern gate of Baron's Hotel. Worried this will devastate evacuation - so many hurt. My heart is with all those injured and killed."

Her colleague, Nus Ghani, said she was on the phone to somebody outside Kabul airport when the blast there took place.

She later said he was "ok" and was heading to a "safe house".

Labour's shadow foreign secretary Lisa Nandy said the reports from Kabul were "devastating".

"This is an appalling and cowardly attack on those already fleeing unimaginable horrors," she added.

"My thoughts are with the Afghan people and the British, US and international personnel who have remained at the airport to save as many lives as possible."

The BBC's Secunder Kermani in Kabul: "Videos shared online show piles on piles of dead bodies, so expect the casualties figures to rise."

Images said to be from the aftermath of the attack outside Kabul airport appear to show injured people with bloodied clothes being moved in wheelbarrows.

Some of the pictures, posted to Twitter by Afghanistan's Tolo news agency, show men, women and children - some with makeshift bandages around their heads - fleeing the scene.

Warning: Some readers may find the following images upsetting.

Afghan journalist Bilal Sarwary - who was evacuated from the country a few days ago - says he has heard from a friend who was in a queue near the airport and had his document approved 15 minutes before the explosion.

He said his friend had witnessed some victims being carried away.

"That tells you that ambulances could not get there," he said.

A Pentagon spokesperson has said that the bombing at Kabul airport has resulted in a number of US and civilian casualties and was the result of a "complex attack".

Prime Minister Boris Johnson will chair a crisis meeting on the situation at Kabul airport on Thursday afternoon, his office says.

French President Emmanuel Macron has said that the situation has "profoundly deteriorated" in Afghanistan.

He called for caution before the situation descended into one "that we can't control" and added that the situation around the airport remains very dangerous.

The initial attack at Kabul airport was followed with a second explosion and small arms fire, the BBC's Jonathan Beale says.

Both explosions took place near the Abbey gate entrance to the airport where large numbers of Afghan refugees have gathered over the past several days.

France's man in Kabul, David Martinon, has appealed to people to get away from the airport gates because of the risk of another explosion.

"To all our Afghan friends," he posted on Twitter, "if you're near the airport gates move away urgently and take cover - a second explosion is possible."

A few moments ago, the ambassador added his thoughts for the victims but said no French officials were hurt. "No French soldier, police officer or diplomat was deployed today at Abbey Gate; #safe"

The Pentagon has confirmed that the explosion at Kabul airport has resulted in an unknown number of casualties.

We reported moments ago that US President Joe Biden had been briefed on the attack at Kabul airport.

It has emerged that Biden was told about the incident during a meeting with security officials about the situation in Afghanistan, Reuters news agency reports.

Afghanistan's Tolo News is reporting that a number of people injured in the explosion at a gate of Kabul airport have been transported to a local hospital.

A Taliban official has said that at least 11 people have been killed in the attack on Kabul airport.

The official said the number included women and children and that a number of Taliban guards had also been wounded.

There is no confirmation.