Knifeman held outside Belgian PM's office was known to police

Brussels, Belgium: A knifeman arrested outside the Belgian prime minister's offices in Brussels this week was known to police and is believed to be mentally unstable, authorities said on Tuesday.

The 29-year-old man, who has not been named, approached two soldiers guarding the building's entrance on Monday morning, made "incoherent remarks" and pulled out a knife, prosecutors said.

The servicemen convinced the suspect to put down the weapon and got him to surrender without further resistance. He was then subdued before police arrived and arrested him.

Prime Minister Alexander De Croo was not at the premises at number 16 on the central Rue de la Loi. No-one was injured in the incident.

The suspect is being investigated for attempted murder and unlawful possession of weapons, said Yasmina Vanoverschelde, a spokeswoman for the Brussels prosecutor's office.

His motives are not yet clear and authorities have requested a psychiatric assessment.

The man was involved in a similar incident in April this year, when, wielding a knife, he attempted to attack a security guard at the US embassy.

"In this case, a judicial investigation had already been opened and the suspect had been forcibly admitted to a psychiatric hospital," said Vanoverschelde.

The US diplomatic compound in the Belgian capital is only a couple of hundred metres from the prime minister's offices.

The area surrounding Rue de la Loi, a major thoroughfare connecting the seat of many European institutions to the Brussels city centre, is dotted with embassies and official buildings.