KRAKOW, Poland/ISACCEA, Romania: Thousands of people crossed into eastern Europe after Russia attacked a Ukrainian base near the border with NATO-member Poland.

The number of refugees fleeing Ukraine since Russia invaded on Feb. 24 climbed to more than 2.8 million, United Nations data showed. This has become Europe’s fastest-growing refugee crisis since World War Two. European Union officials have said 5 million may end up fleeing while others have put the figure higher.

Ukraine said 35 people were killed at the base on Sunday. Moscow said up to 180 “foreign mercenaries” died and a large number of foreign weapons were destroyed.

Millions of people have also been displaced inside Ukraine, with many evacuated only as far as the quieter western regions, including to cities like Lviv.

Polish Prime Minister Mateusz Morawiecki told a news conference with his counterparts from Ukraine and Lithuania that the attack near its border showed Russia wanted to “create panic among the civilian population”. 

Battles continued around many of Ukraine’s main cities, including the capital Kyiv. Ukraine said it would try to evacuate civilians through 10 humanitarian corridors.

Russia denies targeting civilians, describing its actions as a “special operation” to demilitarise and “de-Nazify” Ukraine. Ukraine and Western allies call this a baseless pretext for Russia’s invasion of the democratic country of 44 million.

Ukraine said it had begun “hard” talks on a ceasefire, immediate withdrawal of troops, and security guarantees with Russia. Both sides reported rare progress at the weekend after earlier rounds primarily focused on ceasefires to get aid to cities under siege by Russian forces and evacuate civilians. Those truces have frequently failed.

Authorities and volunteers across central and eastern Europe are scrambling to provide food, accommodation, and medical aid to the millions of refugees pouring across their borders.

Frontline states such as Poland, which has welcomed well over half of the total number fleeing, and Slovakia, Romania, Hungary, and Moldova, have taken in the vast majority of the refugees, some of whom have then headed on further west.

Poland’s border guard said about 1.76 million people had entered the country since the fighting started, with 18,400 arriving during the early hours of Monday.

“We estimate that for sure over 1 million Ukrainians have remained in Poland and we must do everything to ensure their safety,” Polish Deputy Minister of Internal Affairs Pawel Szefernaker said.

Sympathy over the plight of their neighbors and deep-set memories of Moscow’s dominance has seen a groundswell of volunteer efforts. But the sheer scale of the refugee crisis has raised fears of being overwhelmed.

Some countries further away from Ukraine’s borders, such as the Czech Republic, have also taken in tens of thousands of refugees, piling pressure on local authorities, while others, like Lithuania, have only just begun to receive significant numbers.