Hundreds of migrants have crossed from Greece into Macedonia after finding a way through the border fence.
Earlier, some 1,000 migrants, including children, left their sprawling camp in the Greek village of Idomeni and crossed a river near the border.
Some 14,000 people have been stranded at the camp, where conditions have deteriorated following days of rain.
Macedonia last week said it would no longer let any migrants in, blocking the so-called Balkan route north.