Up to 600,000 migrants and refugees are expected to cross from Turkey to Greece and onwards over the next four months, the UN said Thursday, with the flow of people set to persist through the winter. 

"Between November 2015 and February 2016, UNHCR anticipates that there could be an average of 5,000 arrivals per day from Turkey, resulting in up to a total of 600,000 arrivals in Croatia, Greece, Serbia, Slovenia and the former Yugoslav Republic of Macedonia," the UN refugee agency said in a planning document.