Brussels police on Monday detained a Slovakian man dressed in camouflage gear near the European Parliament and found a gun and a chainsaw in his car, triggering a security scare which caused several offices to be evacuated.

The man told police officers that he wanted to meet the European president, prosecutors said.

Parliament spokesman Jaume Duch Guillot said about 500 people were evacuated but two of the three buildings, used only for administrative purposes, have since been declared safe.

The country has been on high alert since mid-January, when police carried out a series of raids, acting on information that a terrorist cell was on the verge of launching an attack. Two suspects were killed in one raid, in eastern Belgium.

The buildings evacuated on Monday include administrative offices and the legislature's visitor centre, the Parliamentarium, spokeswoman Marjory van den Broeke told dpa. The main building was unaffected.

On first inspection, the car in question appeared not to contain explosives, another spokeswoman told Belga news agency. Police and military explosives experts were on site.

Earlier Monday, a suspicious vehicle was spotted near the US embassy in Brussels, Belga reported. The car was later found to have no dangerous items, and the alarm was lifted half an hour later.