UN: Half a million Ukrainians have fled country as refugee numbers are 'rising exponentially'

Some 520,000 Ukrainians have fled their homes since the start of Russian invasion, the United Nations (U.N.) High Commissioner for Refugees said Monday, adding that refugee totals are expected to run in the millions, taxing the resources of neighboring counties.

The figure has grown 10 times since just last week, when the U.N. High Commissioner for Refugees on Friday estimated that 50,000 Ukrainians had left the country. Russia launched its invasion on Feb. 24.

"This figure has been rising exponentially hour after hour, literally since Thursday. I have worked in refugee crises for almost 40 years, and I have rarely seen such an incredibly fast rising exodus of people," Commissioner Filippo Grandi said in a speech before the U.N. Security Council.

The majority of refugees - more than 280,000 - have fled to Poland, while 94,000 have crossed the border into Hungary, roughly 40,000 are in Moldova, 34,000 are in Romania and 30,000 are in Slovakia, while Grandi said tens of thousands have landed in other European countries.

Other estimates indicate as many as 100,000 Ukrainians may be internally displaced.

"We're currently planning, I repeat planning, for up to 4 million refugees in the coming days and weeks. Such a rapid increase would be a huge burden for receiving states and would no doubt stress reception systems and related resources," Grandi said.

"Like all countries, hosting refugees, and around the world, they cannot be left alone to shoulder this responsibility," he added.

Packed roadways stretched for dozens of miles last week as residents sought to flee Kyiv, and U.S. intelligence agencies have assessed that anywhere from 1 million to 5 million Ukrainians could be displaced as a result of the invasion.