Residents of Ukraine's capital, Kyiv, woke to the sound of explosions and sirens, with many now either trying to seek shelter or flee the country.

Some are hunkering down in the city's metro stations and air-raid shelters. But others are trying to escape.

Traffic is jammed on motorways going west out of the capital towards the Polish border.

So on the streets of Kyiv this morning there are two starkly different tempos.

One of them is strangely subdued. Many people are still going to work as normal - trudging the streets and getting on buses.

The other mood is urgent. Many people are forming long queues at banks, supermarkets, petrol stations. Some are fleeing west by car.

'I am ready to fight'

One man stops me in the street and says: "This is war."

Mark, a 27-year-old sales executive had - like us - been woken at around 7am by the sound of blasts and sirens.

He found a young girl in tears downstairs, and took her to the nearest metro station to shelter.

One of Ukraine's 900,000 army reservists, Mark says he is ready to be called up to fight with Russia.

"We don't have another way," he tells me. "We must defend our country. And maybe die in this war."

Mark says he is prepared to be killed fighting for "every millimetre" of Ukraine.

"It's only one way - if our military comes to me and says I must die for my country, I will do it."

'We don't know what to do'

Elsewhere, we meet Svetlana, a school worker who is on her way to an air raid shelter.

After she was woken at dawn "when something went boom", Svetlana took a call from her friends in Russian-annexed Crimea, where Russian tanks have reportedly been crossing into Ukraine.

"It's a war," they told her.

Svetlana quickly packed a bag to take with her to the shelter. It contains a wash kit and a laptop, so she can continue working on her masters degree in psychology.

"We don't understand what we do now - we're going to a place where we can be in safety," Svetlana says.

But she is worried about her family who live in Mariupol, the south-eastern port city where Russian troops have reportedly landed.

"I can't say all what I feel - but it's very, very nervous. I'm very scared."

For many, the safest places to be are metro stations deep under Kyiv.

I meet a couple with a two-year-old who are following news on their phones and trying to work out what to do.

They were scared and didn't speak much English. But I understood when they asked me: "Where are Nato?"

'I want my family to be far from here'

While some are hunkering down in the city's metro and air raid shelters, others in Kyiv are trying to escape. Traffic is jammed on motorways going west out of the capital towards the Polish border.

31-year-old Alex Svitelskyi tells me he wants to get his parents out of Kyiv. He's worried about his sister, too: "I want her to be far from here."

Alex says news of the Russian assault did not come to him as a surprise.

"We all knew that this would happen sooner or later, and I hope that our soldiers are ready because they were preparing themselves," he says.

"We hope that they will hold the line."

But Alex says he fears that if Russian forces do reach Kyiv they will carry out atrocities on its residents, reminiscent of those perpetrated by the Nazis in Ukraine during World War Two.

He says he wants to get his parents away from the capital before it's too late.

"I want them to leave Kyiv to some village, because there will be shelling soon."