A lone gunman armed with grenades opened fire on a square packed with children and Christmas shoppers in the eastern Belgian city of Liege Tuesday, killing three people and wounding 75.

Officials named the gunman - who was himself also killed in circumstances that are not yet clear - as Nordine Amrani, 33, a known criminal who had been summoned by police that morning but who never showed up.

Among the three passers-by killed when Amrani went on his shooting spree near the city's courthouse was a 15-year-old boy who died instantly and a 17-year-old boy and 75-year-old woman who died later in hospital.

Residents shocked

The lunchtime attack sent terrified residents running through the streets for their lives, fleeing into churches and shops as the gunman fired on a crowded square.

"We heard two huge deafening noises and then lots of explosions, people were running everywhere," a baker named only as Patricia said on RTL-TV.

"We closed the door, turned off the lights and hid behind the counter with the customers."

The country's federal crisis centre said it was neither a terrorist incident nor linked to a pending criminal trial.

"It's very difficult to determine the reasons for the attack, but we're investigating all avenues," the centre's Benoit Ramacker told the media.

King and Queen rush to spot

King Albert II and Queen Paola rushed to the scene as did newly-named Prime Minister Elio Di Rupo and Belgium's Home Affairs Minister Joelle Milquet broke off European Union talks and too was headed for Liege.

"It's uncertain yet whether he (Amrani) killed himself or whether his weapons exploded," public prosecutor Danielle Reynders told a news conference.

"He left his home this morning with his backpack and his arms," she said, adding that he climbed on to the roof of a bakery shop ‘and fired and then threw three grenades’.

Hours later groups of people sat weeping on sidewalks amid the screech of ambulance sirens and the roar of helicopters. Pools of blood lay on the streets.

The shooting took place around noon on Saint-Lambert square, home to the courthouse and located near a busy Christmas market in the town of 196,000 people.

Some initial reports said it was a foiled bid to rescue a suspect from the courthouse.

Killer a known criminal

Police had raided Amrani's Liege home recently seeking cannabis plants but had found weapons instead. In 2008 he was sentenced to almost five years behind bars for illegal possession of arms and growing cannabis.

In September 2008 he was thrown behind bars for 58 months when police uncovered a weapons arsenal in his home.

They foung 10 firearms and 9,500 gun parts along with 2,800 cannabis plants, but a prison official said Amrani was granted early release last year.

A weapons afficionado, he was said to be able to dismantle, repair and put together all sorts of weapons but was never linked to any terrorist act or network.

Reynders said although the gunman had a record for drugs dealing, arms possession and holding stolen goods, there had never been a sign he was unbalanced in any way.

There was much initial confusion over the shooting as events unfolded, with initial reports of more than one gunman.

Journalist Nicolas Gilenne told AFP he had just left the courthouse where he was covering a trial when the attack began.

"I saw a man wave his arm and throw something at the bus shelter. I heard an explosion. He turned around, picked something else up, pulled the pin. I started to run. He was alone and seemed very much in control.”

"He wanted to hurt as many people as possible. I heard four explosions and shots during about 10 seconds."

Residents had earlier told local television that shots were fired across the square by gunmen posted on the rooftop of a bakery and grenades hurled at bus shelters and into the courthouse.

Reports had also said that two to three gunmen armed with either explosive flash grenades or killer defensive grenades were involved.

"The city centre is completely cordoned off. People are sheltering in shops or in buildings. Police are in position," said a town hall employee contacted by AFP who asked not to be identified.

"Luckily the mayor had postponed the opening of the Christmas market due to bad weather and high winds. Otherwise many more would have died," the employee added.