Ukraine’s army is trying to repel a full-scale Russian invasion, with fierce battles taking place close to the capital Kyiv.
Fighting is raging at an airfield on the outskirts of the city, and it could become a springboard for the Russian army into Kyiv if its troops seize it.
The Russian assault is being fought on several fronts after it attacked from the east, north and south on Thursday.
Kyiv has been hit by blasts, and at least one block of flats was damaged.
There are also reports of gunfire inside the city and on its northern outskirts, amid Ukrainian government warnings that “saboteurs” may already be operating inside the city.
Overnight, families took shelter in Kyiv’s metro stations as aerial attacks struck the city, including the densely-populated Pozniake area, injuring at least eight.
“Putin, we want to see you slaughtered like an animal,” one Kyiv resident told the BBC’s Nick Beake.
Ukrainian officials said there had been missile strikes on the city and a Russian aircraft had been shot down.
“They [the Russians] say that civilian objects are not targets. It is a lie,” Ukraine’s President Volodymyr Zelensky said in a video released early on Friday. “The reality is that they don’t see a difference in which areas they target.”
Ukraine says at least 137 people – civilians and soldiers – have been killed, with UN estimates suggesting more than 100,000 people have already fled from their homes. Overnight, at least 1,000 Ukrainians arrived by train in Poland’s south-eastern city of Przemysl alone.
British Defence Minister Ben Wallace said the UK estimated Russia had lost 450 personnel since Moscow launched the offensive in the early hours of Thursday morning.
President Vladimir Putin – who declared war in a dramatic televised address – has threatened any country attempting to interfere with “consequences you have never seen”.
Russia attacks Ukraine: More coverage
Air and missile strikes have rained down on cities and military bases, with tanks rolling in across three sides of Ukraine’s vast border. It followed weeks of escalating tensions, as Russia massed troops around the country.
Western intelligence officials earlier warned that Russia was building an “overwhelming force” to take control of the city.
In the face of stark odds, Ukraine’s President Zelensky has vowed to continue fighting. He said “a new iron curtain” was falling into place and his job was to make sure his country remained on its western side.
There have already been stories of immense bravery – including that of 13 border guards on a tiny island in the Black Sea who refused to surrender to a Russian warship and were massacred in a bombardment.
President Zelensky said they would be given posthumous war hero honours.
Thursday also saw fighting around the site of the former nuclear power plant in Chernobyl. Ukrainian presidential adviser Mykhaylo Podolyak said the nuclear site itself had been lost following a “fierce battle”.
Mr Zelensky ordered conscripts and reservists in all of Ukraine’s regions to be called up to fight. The country’s defence minister urged anyone who was able to hold a weapon to join the effort to repel Russia.
Human rights groups warned prior to the invasion that an attack could trigger a major refugee crisis in Europe.
Western leaders expressed shock and anger at the scale of the attack. The UK, EU and other allies vowed to impose tough new sanctions to punish Moscow but said they would not send in troops.
French President Emmanuel Macron held a telephone call with his Russian counterpart, in what was Mr Putin’s first conversation with a Western leader in days.
Mr Macron demanded an “immediate halt” to the offensive and threatened Mr Putin with “massive sanctions”, the French government said. The Kremlin, however, simply said the pair had a “serious and frank exchange of views”.