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The number of refugees leaving Ukraine is soaring towards one million as fighting intensifies and spreads.
As of Wednesday, 874,026 refugees had left Ukraine with more heading for its borders, the UNHCR refugee agency said.
Poland alone took in more than half of them – 453,982 – as the rate of refugees escaping notched higher.
The new figure is a marked leap from the estimated 677,000 announced on Tuesday afternoon and the 520,000 from Monday.
“We are looking at what could become Europe's largest refugee crisis this century,” UNHCR chief Filippo Grandi said.
The first wave of people fleeing Ukraine is likely to be those with cars, resources and some connections in other European countries, he said.
If Russia's military offensive continues and more urban centres are hit, people who are “more vulnerable in every respect” could start to flee, he said.
Kharkiv police building in flames after Russian missile strike
UNHCR figures show about 116,000 fleeing to Hungary; 67,000 to Slovakia; 79,315 to Moldova; 42,900 to Russia; 44,540 to Romania; and 341 to Belarus.
About 96,000 crossed into Russia from the separatist Donetsk and Luhansk regions between February 18 and 23, the UNHCR noted.
Meanwhile, 69,600 have moved on to other European countries.
The EU has been trying to push an open-door policy for Ukraine refugees but data from individual nations is not yet readily available.
In Germany, 5,309 people have been registered as entering Germany from Ukraine, according to the federal police, but the number could be much higher.
“There are no border controls, at least no regular border controls, only random checks. That's why it is very possible that significantly more people have already reached Germany,” an interior ministry representative said.
In Ireland, 134 refugees have arrived and Irish Foreign Affairs Minster Simon Coveney said up to 20,000 may eventually arrive.
Prime Minister Boris Johnson has indicated that the UK, no longer a member of the EU, could take in about 200,000 Ukrainian refugees and has encouraged requests from those with relatives already in the country.
The UNHCR projects that more than four million Ukrainian refugees may eventually need protection and assistance in neighbouring countries.
“The military offensive in Ukraine has caused destruction of civilian infrastructure and civilian casualties and has driven many thousands of people from their homes seeking safety, protection and assistance,” it said.
“There is a clear indication that many more people are on the move. They are in need of protection and support.”
The UN on Tuesday launched an emergency appeal for $1.7 billion to provide urgent humanitarian aid to those caught up in the Russian invasion of Ukraine and for the refugees fleeing the violence.
Mr Grandi said $550.6 million of that was needed to help refugees across the region, with the aim to provide shelter, emergency relief items, cash assistance and psycho-social support.
The Polish rail company PKP Intercity said on Saturday it would carry Ukrainian citizens free of charge from the border. Deutsche Bahn is giving Ukrainian passport or ID-card holders free travel on its long-distance trains from Poland to Germany.
Eurostar is offering Ukrainians travelling with valid visas free rides to the UK from its stations in France, Belgium and the Netherlands.
More than a dozen telecom providers are providing free international calls to Ukraine or are scrapping roaming charges there.
Airbnb is working with its hosts to house up to 100,000 Ukrainian refugees free of charge. Polish hospitality chain Arche Hotels has lodged 1,000 refugees and is preparing to admit 5,000.
