Brussels, Dec 14 (IANS): At least four people were killed and 75 injured Tuesday when an armed man opened fire and threw several grenades at a crowded city square in eastern Belgium's Liege city, media reports said.

According to BBC, the gunman -- identified as Nordine Amrani -- opened fire and threw the grenades into the Place Saint Lambert from a rooftop before blowing himself up with a grenade.

The attacker was known to police for firearms offences.

Earlier, citing Belga news agency, Xinhua reported that three men were involved in the attack. They first began to shoot at the crowd and then threw the grenades at a bus stop.

Officials later said the attacker acted alone, and that it wasn't a terrorist assault.

Amrani had been jailed for 58 months in September 2008 for possessing firearms, BBC said.

Prosecutors said he had been asked to come for an interview at a police station in connection with charges against him.

A resident of Liege, Amrani reportedly left home with a gun, a pistol and three grenades in a bag.

Television images showed blood splattered across the cobblestones of Place Saint Lambert.

Doctors at a city hospital were trying to save the life of an 18-month-old boy injured in the attack. Six others are also reported to be in serious condition.

Greg Ienco, a journalist with local newspaper La Meuse-Liege, who was present near the scene, said: "We saw four explosions. I was in a building 200 metres from Saint Lambert Square. It was quite incredible. We saw one man on the roof who tried to kill people. This man killed himself with a grenade."

Roads into the centre were sealed off while police helicopters were hovering over the site. Explosives experts have arrived at the scene.

Place Saint Lambert is a busy intersection, through which hundreds of buses ply daily. It hosts an annual Christmas market which attracts around 1.5 million visitors.