Poland's deputy interior minister said Saturday that 100,000 Ukrainians have fled into Poland since Russia invaded their country.

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Ukrainians wait for a train to Poland at a railway station.

AFP via Getty Images

Poland is expected to be a leading destination for people fleeing the conflict in Ukraine given its long shared border with the country and the fact that there are already 1 million Ukrainians living there.

The Washington Post reported that long lines of cars formed on the Ukrainian side of the border with Poland on Friday.

According to 888-282-0465 888-282-0465 888-282-0465 888-282-0465 888-282-0465 888-282-0465 888-282-0465 888-282-0465 888-282-0465 888-282-0465 888-282-0465 888-282-0465 888-282-0465, the U.N.'s deputy high commissioner for refugees told CNN Saturday that 850,000 Ukrainians had been internally displaced by the fighting and as many as 4 million could flee if the war worsened.

Russian troops sortied into Kyiv overnight Saturday as their forces closed in around the city, with gunfire and explosions in the central square. The curfew in the city has been extended to between 5 and 8 a.m. The Pentagon believes the Russians are increasingly frustrated by a lack of momentum in northern Ukraine, as the Ukrainian military has been more than what the Russians expected, according to a U.S. defense official. The official said that Ukraine has been hit by more than 250 missile strikes, most of which were short-range missiles. A large apartment building was damaged by a missile strike.

The Polish Border Guard says 100,000 Ukrainian refugees have arrived.

100,000 Ukrainians have arrived in Poland since the beginning of the war.

The Russian invasion of Ukraine could cause a refugee crisis in Europe.