A crowd of migrants has broken down a barbed-wire fence on the Macedonia-Greece border using a steel pole as a battering ram.

TV footage showed migrants pushing against the fence at Idomeni, ripping away barbed wire, as Macedonian police let off tear gas to force them away.

A section of fence was smashed open with the battering ram. It is not clear whether any migrants got through.

Many of those trying to reach northern Europe are Syrian and Iraqi refugees.

About 6,500 people are stuck on the Greek side of the border, as Macedonia is letting very few in. Many have been camping in squalid conditions for a week or more, with little food or medical help.

The chaos on Monday erupted at a gate festooned with barbed wire, keeping migrants away from a railway line.

The protesters shouted "Open the border!" and threw stones at Macedonian police, who responded by firing rounds of tear gas to prevent them from getting through.

Macedonia and some other Balkan countries have erected fences in an attempt to reduce the influx of migrants, after more than a million reached Germany last year.

Greece is angry with Austria for having imposed a cap on migrant numbers. The crisis has left Greece shouldering much of the burden of housing migrants arriving in the EU from Turkey.

Many are refugees fleeing war in the Middle East, while others are escaping human rights abuses in Afghanistan, Eritrea and other conflict zones.