Macedonia briefly opened its border with Greece to refugees on Wednesday, allowing 240 people from Syria and Iraq to cross into the country.
The crossing was open from Tuesday midnight to 2am Wednesday, and from 7am to 9am Wednesday, said Greek police.
Hundreds, including many families with children, arrive daily at the Idomeni crossing in northern Greece, where thousands of refugees set up tents in fields all around as the two official camps are overpopulated.
At least 22,000 refugees have been stranded in Greece in the past week since border restrictions imposed by the countries along with the Balkan corridor which is used to get to central and northern Europe.
More than 7,000 mostly Syrian and Iraqi refugees have been stuck in Greece at the Idomeni border in deteriorating conditions, for more than a week, after Macedonia, and other Balkan countries including Serbia and EU members Slovenia and Croatia imposed a daily limit on the number of refugees allowed to enter.
The Idomeni crossing had been closed for nearly 24 hours, following clashes when hundreds of refugees tried to force their way into Macedonia whose police responded with tear gas and stun grenades on Monday.
The build-up of thousands of migrants and refugees on Greece's northern border is fast turning into a humanitarian disaster, the United Nations said on Tuesday as the European Union prepared to offer more financial aid.
German Chancellor Angela Merkel said clashes at Greek border with Macedonia on Monday - when refugees battered down a gate and were tear-gassed - simply underlined the urgency with which the EU needed to act on the crisis.
The refugees in Macedonia aim to take a train to go to Hungary via Serbia as Macedonia is a passage to Greece, Germany, Hungary and Serbia.
The attraction of Hungary is that it is a member of the European Union and more importantly it is a Schengen Zone state. Refugees in order to travel around EU countries must enter a Schengen zone member country.
Macedonia has constructed two lines of razor wired fences along the border in early February after Austria urged it to be prepared to “completely stop” the influx of refugees across its southern border from Greece.
The head of Europe's border control agency Frontex says the numbers of refugees crossing into Europe in January and February this year was thirty times higher than the levels reached at the same time last year with 131,000 refugees.
Macedonia says it will only allow in as many refugees as Serbia, its northern neighbor, takes each day. The tiny trickle has caused a huge backlog in Greece, where most refugees reach Europe.
According to the International Organization for Migration (IOM), more than 1.1 million refugees arrived in Europe last year, more than 850,000 of those arrived by sea to Greece from Turkey.