WARSAW - The number of people who have fled Ukraine to escape Russia's invasion has passed 6 million in Europe's worst refugee crisis since the end of World War Two, U.N. refugee agency said on Thursday.

Russia's invasion, which started on Feb. 24, has triggered a massive displacement of people, including more than 8 million Ukrainians within the country. U.N. data showed that 6.03 million had fled Ukraine as of Wednesday.

Most have crossed to the European Union through border points in Poland, Slovakia, Hungary and Romania.

(Reporting by Anna Wlodarczak-Semczuk in Warsaw; Editing by Toby Chopra)