Some 5,600 people crossed into Macedonia from Greece on Thursday, a jump over previous days that highlights the ever-rising numbers of migrants moving through Europe, the UN said on Friday.

"Yesterday (Thursday) 5,600 people crossed from Greece into the former Yugoslav republic of Macedonia," said UN refugee agency spokeswoman Melissa Fleming.

"It is an absolutely dramatic situation," she added, stressing that Macedonia remains a transit country, with most migrants who enter seeking to move elsewhere.