The time is 04:00 in the Ukrainian capital as day eight of the Russian invasion begins.

Here's what you need to know:

• Massive explosions have been heard in Kyiv in the past hour, with footage posted on social media showing an enormous fireball lighting up the night sky
• The International Criminal Court in The Hague has opened an investigation into alleged war crimes by Russia
• The United Nations says the number of refugees fleeing Ukraine has now reached one million
• Ukraine President Zelensky released a video, calling on citizens to do everything they can to resist the Russian occupation
• US officials say a 40-mile (60km) Russian armoured convoy is somehow "stuck" on its way to Kyiv.
• Witnesses say Russia's artillery bombardments have increased in the past 24 hours and fierce fighting is continuing.

• Russian troops have surrounded the strategic port cities of Mariupol and Kherson

• Kherson's mayor said Russian troops had entered the city, but that it would remain for now under the Ukrainian flag
• In the northern city of Chernihiv, Ukrainian officials said a hospital was hit by two cruise missiles
• In Kharkiv, Ukraine's second largest city, Russian shells continued to fall, reportedly killing and wounding dozens of civilians

The United Nations says one million refugees have now fled Ukraine to neighbouring countries.

The exodus has taken place in just seven days. The Russian invasion began last Thursday.

As the BBC's Lewis Goodall points out: "The refugee crisis of 2015 involved 1.3 million. That's nearly been surpassed by the numbers from Ukraine in a week."

In a statement on Twitter, UN High Commissioner for Refugees Filippo Grandi pleaded for "guns to fall silent, so that life-saving humanitarian assistance can be provided" to the millions who remain in the country.

The agency has predicted the conflict will leave some 12 million people internally displaced and in need of relief.

Here's more on where Ukrainians are fleeing to and how neighbouring countries are helping them.

CBS News international correspondent Charlie D'Agata was broadcasting live from a rooftop in Kyiv when explosions shook the city.

The veteran reporter initially mistook the explosion for lightning before the sound reached the news team seconds later.

Image source, Getty Images

The Swift banking system has said it will disconnect seven Russian banks from its global network on Saturday 12 March to "comply with applicable sanctions laws".

"Our deepest thoughts are with those suffering the tragic human consequences of Russia’s invasion of Ukraine," a statement from the organisation reads.

Earlier this week, Western nations agreed to exclude some key banks from the international payment system.

Swift is used by thousands of financial institutions in more than 200 countries to facilitate cross-border flows of money.

Image source, Swedish Armed Forces

The Swedish Armed Forces say four Russian fighter jets violated a ban on the use of its domestic airspace on Wednesday.

The Scandinavian nation - which is not a Nato member - closed its airspace to Russian aircraft on Monday, in line with similar measures by other European nations.

In a statement, Sweden's military condemned the alleged incursion by the Russian warplanes as "unprofessional and irresponsible".

But it noted the incident, said to have taken place over the Baltic Sea, was brief.

Former US General David Petraeus says Russia would have had absolute supremacy in the air over Ukraine if the West had not sent air defence weapons, supplies and missiles early on.

"Russians should have been able to just fly at will, but they are not, because of these systems," Petraeus told BBC World News.

He said multiple verified reports of downed planes suggest Russian forces have suffered "very significant losses".

Image source, Facebook

Ukraine's president released a new video message to citizens on Wednesday night, urging them to keep up the fight against the Russian invaders.

The video, posted on Facebook, has the caption: "Every occupier should know: they will receive a fierce rebuff from the Ukrainians.

"We are a nation that broke the enemy's plans in a week," the democratically elected president said from an undisclosed location.

"But we stopped them."

He said captured Russian servicemen "do not know why they are here", and that enemy soldiers are "fleeing back to Russia".

He added that the troops are "confused children", who are being "used" by their leaders in Moscow.

Zelensky also thanked civilians in the cities of Konotop, Bashtanka, Energodar and Melitopol, who he said had blocked roads to Russian troops.

He added that he has recently spoken to the leaders of Norway, Israel, Kazakhstan, Qatar, Canada, Poland and the European Council.

He also signed a decree conferring the title of Hero of Ukraine on 15 Ukrainian servicemen, nine of them posthumously.

At least four explosions have just been reported in Ukraine's capital city, where it is in the early hours of Thursday.

Two powerful blasts reportedly went off in the city centre, followed by two more near a metro station. Air raid sirens have been heard wailing.

The Twitter account of OSINTtechnical, which shares open source intelligence, released a video of one explosion.

The BBC has not independently verified this footage.

The small city of Irpin, near the Ukrainian capital Kyiv, has been devastated by Russian attack since the invasion began last week, say Ukrainian authorities.

Here's what a residential neighbourhood in Irpin looked like before and after a recent missile strike:

Kostas Kallergis
BBC News, Moldova

In Moldova’s main exhibition hall, hundreds of tiny cubicles are portioned out between newly arrived Ukrainian families.

Sheets and towels are draped over the entrances to give a vague sense of privacy; tricycles and prams clog the corridors outside.

Marina, 60, has been living in one of the cubicles since Saturday night, sharing it with her Bible and her memories.

She worked in a coal mine in the Donbas region of Ukraine until fighting broke out in 2014 and she fled to Odesa.

When Russian bombs fell on Odesa last week, she fled again.

"I’m tired of running from the war," she told me.

"Eight years we’ve been running. We’re mentally exhausted. If only God would help us, and give us peace, everyone could live a normal life.

"But now everyone in the world is trembling.”

Image source, Getty Images

Russian state-owned media outlets RT and Sputnik have been stopped from broadcasting across Europe, after being banned by the EU - which accused them of spreading disinformation and propaganda.

RT has also dropped off air in the UK, because its feed comes via Europe.

It comes as the UK's communications regulator Ofcom launches another 12 investigations into RT, taking the total to 27.

Ofcom will consider "whether RT should retain a UK licence" and if it has met due impartiality rules.

The EU said the two channels promoted “systematic information manipulation by the Kremlin”.

Although the UK is no longer in the EU, it's still affected by the decision, because the sanctions were applied to the satellite companies in Luxembourg and France, which provided the feed to Sky, Freesat and Freeview.

Read more: Watching the war on Russian TV - a whole different story

No easy off-ramp for Putinpublished at 23:50 Greenwich Mean Time 2 March 2022

23:50 GMT 2 March 2022

Lyse Doucet
Chief International Correspondent

Image source, Getty Images

From the very beginning - even before this seven-day invasion - Russia's intentions were a guessing game.

Before the war started people would say: "Will President Putin actually invade?"

People also said: "If he does invade, maybe what he really wants is a corridor in the south to connect the areas that were already annexed or moved into in 2014."

But now his forces are attacking, and if the reports from Kherson are to be believed, he is taking over areas of Ukraine.

It's difficult to see how this will all end.

How do you find what we call a 'face-saving device' when this war is against a country that Putin says shouldn't exist, against a government he describes as being run by neo-Nazis and criminals and a puppet government for the West?

This conflict isn't about a war aim. It’s about restoring the lost glory of the Soviet Union.

So it's very hard to see how Ukraine, Russia and the rest of the world find a way out.

Image source, Getty Images

Credit agency Fitch has downgraded Russia's sovereign credit rating from BBB to B, and labelled the country "rating watch negative", citing the growing international sanctions campaign against Moscow.

The sweeping sanctions on the Russian economy are likely to affect Moscow's ability to pay off its debts, Fitch added in a statement.

The downgrade comes as the World Bank ends all programmes in Russia and Belarus because of "hostilities against the people of Ukraine".

Image source, Getty Images

Up to 15,000 people are now taking shelter in Kyiv metro stations, according to the official in charge of the city's subway.

Viktor Brahinsky told Ukrainian media that the underground can accommodate up to 100,000 people.

He added that the system currently has water and bathrooms, as well as food and medicine.

"Many people have nowhere to go. A few metres on the floor and a blanket have become their only home," he said, reports the BBC Ukrainian Service.

"We urge people to bring warm clothes, food and support for those around them - especially women with small children and the elderly," he added.

Foreigners, particularly African and Asian students in Ukraine, have raised concerns over the past few days that they are being discriminated against and turned back at the border.

Now Ukraine's foreign ministry says it has launched an emergency hotline for such students wishing to leave.

It said border checkpoints were operating 24 hours a day and people of all nationalities would be processed on a "first come first served approach".

Image source, Getty Images

The chief prosecutor of the International Criminal Court has announced he has opened an investigation into potential war crimes by Russia during its invasion of Ukraine.

Karim Khan wrote that in a "preliminary examination of the Situation in Ukraine, my Office had already found a reasonable basis to believe crimes within the jurisdiction of the Court had been committed, and had identified potential cases that would be admissible".

The chief prosecutor said on Monday he intended to seek authorisation from the court's presidency to open the inquiry, but a referral by the UK and 38 other nations to the court meant he now intended to launch the investigation immediately.

Image source, Reuters

The UN human rights office says 227 civilians were killed in the first five days of the Russian invasion of Ukraine.

Officials say another 525 civilians have been injured across Ukraine during the conflict.

"Most of these casualties were caused by the use of explosive weapons with a wide impact area, including shelling from heavy artillery and multi-launch rocket systems, and air strikes," it said in a statement issued in Geneva.

The organisation says it believes the true death toll is "considerably higher", especially in government-controlled territory, because of reporting delays.

Image source, Getty Images

The Pentagon has delayed this week's scheduled test launch of a Minuteman III intercontinental ballistic missile.

The move will signal "how seriously we take our nuclear responsibilities at a particularly tense time", spokesman John Kirby told reporters on Wednesday.

Over the weekend, Russian leader Vladimir Putin placed his country's nuclear forces on high alert.

Kirby said the US has not taken any similar steps, slamming Putin for "his unhelpful and unnecessary rhetoric".

He stressed the postponement would not impact America's nuclear posture or readiness in any meaningful way.

Several ICBM tests take place in the US each year and are often planned a few years in advance.

Image source, Getty Images

More now on the news that Russia has been referred to the International Criminal Court (ICC) by 38 different countries over suspected war crimes committed during its invasion of Ukraine.

In a statement issued on Wednesday evening, the UK foreign office said that it has "led efforts to bring together allies", including all 27 members of the EU, Canada, New Zealand and Switzerland, to report Vladimir Putin's regime to the court.

Dominic Raab, the UK's Deputy Prime Minister and Justice Secretary, said in a statement: "As a founder member of the International Criminal Court, the UK is willing to provide the necessary technical assistance to support successful convictions."

"Any Russian leader or officer carrying out orders that amount to war crimes should know they face ending up in the dock of a court and ultimately in prison," Raab added.

Foreign Secretary Liz Truss said that Putin's regime has "indiscriminately" targeted civilians and added the "UK will work closely with allies to ensure justice is done".

While Russia is a signatory of the Geneva Convention, the international treaty that defines war crimes, it withdrew from the ICC in 2016 after it classified the annexation of the Crimean Peninsula as an occupation.

It means that individuals charged by the court will have to be detained in countries that accept its jurisdiction, perhaps confining Putin to Russia and allied states for the rest of his life.

Image source, Getty Images

The BBC has launched a new shortwave radio service in Ukraine to ensure the resilience of its news operations in Ukraine and Russia, the corporation has announced.

The new broadcasts will make four hours of World Service English news available every day and will reach audiences in Ukraine and parts of Russia.

Listeners in the area will be able to tune into the broadcasts at 15735 kHz from 16:00-18:00 GMT and 5875 kHz from 22:00-00:00 GMT.

Director-General Tim Davie said in a statement: “It’s often said truth is the first casualty of war. In a conflict where disinformation and propaganda is rife, there is a clear need for factual and independent news people can trust – and in a significant development, millions more Russians are turning to the BBC.

“We will continue giving the Russian people access to the truth, however we can."

Throughout the conflict, the BBC's Ukrainian and Russian services are also providing live updates online.