BEREGSURANY, Hungary (AP) — The mass exodus of refugees from Ukraine to the eastern edge of the European Union showed no signs of stopping Monday, with the U.N. estimating that more than 500,000 people have already escaped Russia's burgeoning war against Ukraine.

Long lines of cars and buses were backed up at checkpoints at the borders of Poland, Hungary, Slovakia, Romania and non-EU member Moldova. Others crossed the borders on foot, dragging their possessions away from the war and into the security of the EU.

Several hundred refugees were gathered at a temporary reception center in the Hunga...