AFP/Roszke, Hungary

Hungarian police on Wednesday fired tear gas and water cannon at several hundred migrants protesting at being unable to cross the border from Serbia, AFP reporters said.

"The crowd on the Serbian side became aggressive and threw stones, bottles and sticks at police on the Hungarian side," a police statement said.

A video showed the migrants opening a gate at the border before retreating.

Police said they had called in reinforcements to handle the crowd, noting that the barrier was "replaced by several ranks of police".

"The police is protecting the border of Hungary and the EU while respecting the law and the principle of proportionality," it added.

An AFP reporter on the Serbian side said around 300 out of a group of 500 took part in the protest and confirmed that some were hurling objects at the police.

Police fired at least 20 tear gas grenades as the crowd chanted slogans in Arabic with their fists in the air.

Children were crying from the effects of the tear gas, which causes respiratory problems as well as eye irritation. Several ambulances arrived at the scene.

There was also two helicopters flying overhead, one from the army and the other from the police.

The incident happened at "Roszke II", an official border crossing point between Serbia and Hungary.

The clashes took place after Hungary sealed its southern border with Serbia, cutting off one of the biggest entry points for migrants into the European Union this year.

Serbian police could be seen holding handkerchiefs over their mouths because of the tear gas.

Speaking to the M1 TV news channel, Hungarian Foreign Minister Peter Szijjarto said he had asked Belgrade to have the Serbian police take action to quell the disturbances.