More than 2.5 million people have fled Ukraine, U.N. agencies said on Friday, and a further 2 million have been driven from their homes within the country since the start of a Russian invasion on Feb. 24.

The United Nations has been planning its humanitarian needs on the assumption that some 4 million Ukrainian refugees would seek safety abroad.

However, with around 200,000 people having fled to neighbouring countries over the past 24 hours, a U.N. refugee official said they may have to revise that figure higher.

“It is quite possible that planning figure of 4 million will be revised up. That wouldn’t be a surprise,” Matthew Saltmarsh, a spokesperson with the U.N. refugee agency (UNHCR) near the border in Poland told Geneva journalists via videolink.