Bomb disposal experts are investigating two suspect vehicles containing gas bottles near the US embassy in central Brussels, a Belgian Defence Ministry spokesman said.
"As far as I know there are two suspect vehicles, one close to the American embassy and one close to the Belgian Defence Ministry," said ministry spokesman Didier De Weerdt.
"Apparently there are gas bottles inside the vehicles."
He said several buildings had been evacuated between the embassy and the ministry and a bomb disposal squad was assessing the vehicles. Police have closed several of the main routes through the district and out of the city centre.