The United Nations High Commissioner for Refugees says more than 4 million people have fled Ukraine for other countries because of the Russian invasion.

Vlad Braun is one of around 2 million children who have left Ukraine. The 12-year-old and his grandparents arrived in Japan last month to stay with his aunt near Tokyo.

His school resumed classes online, so his classmates can participate from countries such as Poland and Italy.

But Braun said his classes could be canceled if Internet access is cut off because of the situation in Ukraine.

Braun said, "I'm worried about my family members and friends who remain in Ukraine. I want to see the war end as soon as possible."

Japan's Foreign Minister Hayashi Yoshimasa visited a facility for evacuees in Poland on Saturday. More Ukrainians have crossed into Poland than any other country.

The Japanese government is planning to bring around 20 Ukrainians to Japan on Hayashi's return flight.