BRUSSELS, May 29 (Xinhua) -- The knife attack and shooting that left two patrolling police officers and one passenger in a car killed in eastern Belgian city Liege on Tuesday is being investigated as a suspected terrorist attack, according to authorities.

At about 10:30 a.m. local time (GMT 0830), two police officers performing routine patrols in the center of Liege were attacked by a knife-wielding man, who snatched the gun from one of the police officers and proceeded to kill them both, Liege's prosecutor Philippe Dulieu told a press conference.

During his escape, the man attacked a vehicle and shot dead a young occupant in the car. He then went on his way and went into a local high school where he took hostage a lady who works there.

Then the security personnel intervened and the assailant made an exit from the building by firing on the police and was shot dead. During the exchange of fire, two police officers were injured.

The investigation has been taken over by the Belgian Federal Procuratorate, as the evidence clearly indicated that it was a "terrorist attack", according to officials.

Local media reports identified the attacker as a man who was born in 1982 and had just taken leave from prison on Monday evening. He had been sentenced to prison for numerous crimes such as theft and drug trafficking, according to reports.

Reports said since the man had no affiliation to terrorist groups prior to his incarceration, he is likely to have been brainwashed with extremist ideology while serving his time in prison.

In an interview with the media, Belgian Prime Minister Michel expressed condolences and sent his warmest wishes to the victims and their families.

The Belgian threat assessment coordination agency (OCAM) announced on the same day that the Belgian national security alert level will remain unchanged until further notice.