Refugees wait outside a newly opened registration center in Brussels on Monday, under the watchful eyes of police. Thierry Monasse/VCG

Refugees from Ukraine packed the entrance of the registration center in Brussels on Monday. More than 3 million people have fled Ukraine since the war began, according to the U.N. Photo: Dursun Aydemir/VCG

Volunteers provide administrative support to refugees at a registration center on Monday. Photo: Thierry Monasse/VCG

Children are kept occupied with toys at a refugee registration center Monday, while their parents complete the administrative process. Photo: Thierry Monasse/VCG

Children from Ukraine find solace at a temporary shelter in Krakow, Poland, on Wednesday. Photo: Omar Marques/VCG

Refugees fill out registration documents in Krakow on Wednesday. An estimated 1.8 million people have fled to Poland, a tracker provided by the U.N. showed. Photo: Omar Marques/VCG

In Berlin, refugees queue for food on March 8 after arriving at a reception area of a train station. Photo: Michael Sohn/VCG

Evacuees from the Donbas region arrive at a railway station in Rostov-on-Don in southern Russia on Wednesday. Photo: Erik Romanenko/VCG

Displaced Ukrainians aboard a Poland-bound train departing from Lviv on Sunday. Photo: VCG

A group of Ukrainian civilians walk along a train station platform in Lviv on Wednesday. Photo: Aleksey Filippov/VCG