Macedonian authorities have briefly opened their border with Greece to refugees heading for central Europe, allowing in a few score.
About 10,000 people remain camped at the crossing, awaiting their turn.
Greek police said Macedonia opened the crossing from midnight on Tuesday to 2am on Wednesday, and from 7am to 9am on Wednesday, admitting 170 people from Syria and Iraq.
Hundreds, including many families with small children, arrive daily at the Idomeni crossing in northern Greece, where two official camps are so full that thousands have set up tents in fields all around.
Macedonia has said it will only allow in as many refugees as Serbia, its northern neighbour, takes each day. The tiny trickle has caused a huge backlog in Greece, where most refugees and other migrants reach Europe.