An attacker has tried to crash his car through the gates of an army barracks in southern Belgium but fled in the vehicle after shots were fired, a government official says.

The incident occurred near the French-speaking town of Namur, south of Brussels. The suburb of Flawinne is the site of one of Belgium's major military barracks, home to the 2nd Commando Battalion.

Defence Cabinet chief Lt Gen Claude Van De Voorde told The Associated Press: "One car tried to get into the barracks. There was one person in the car. He fled."

He could not confirm media reports that there were explosives in the car. "People start making up things quickly," Gen Van De Voorde said.

Since the May 2014 attack by a lone gunman on the Jewish museum in Brussels in which four people were killed, Belgium has been on high alert for further extremist attacks.

In January, police killed two men and arrested a third in a counter-terrorism raid in the eastern city of Verviers against a group suspected of plotting a major attack.

Belgium has been one of the largest recruiting bases per capita for foreign fighters travelling to join the Islamic State, and authorities have openly expressed alarm about what the recruits might do if they return home.

A preliminary report this month from a UN Working Group on the Use of Mercenaries estimated 500 people have been recruited from Belgium to fight in Iraq and Syria.