Brussels, May 30 (IANS): The man who shot dead two police officers and a civilian in the Belgian city of Liege had killed someone before the attacks, the country's Interior Minister said on Wednesday.

Minister Jan Jambon said the gunman, named as Benjamin Herman, had killed another person the night before the attack, a man believed to be a heroin user whose body was found early Tuesday at his home in the eastern village of On, the BBC reported.

Hours later, the attacker stabbed two police officers from behind, took their firearms, and shot them and a civilian.

The attacker then ran into a nearby school and took a woman hostage before he was killed during a rescue operation mounted by special forces. Police sources quoted in local media said the man was heard shouting "Allahu Akbar" ("God is greatest" in Arabic).

Jambon said the hostage, believed to be a cleaner, prevented more deaths by talking the gunman around.

"She was very courageous and perhaps, but this we will have to verify, she helped avoid more victims in the school," said Jambon, who visited the woman in hospital, where she was being treated for shock.

Herman, a prisoner on 48-hour leave, bludgeoned to death a former cellmate with a blunt object at his home on Monday evening before "hunting" police officers the next morning, the minister said.

Belgian authorities launched a terror investigation and were also probing why Herman was allowed temporary leave from prison.

The 36-year-old had a lengthy criminal record including theft, assault and drug charge convictions and had been flagged in three reports on radicalism.

Belgium did not raise its terror threat level following the attacks, described by Jambon as an "isolated case".

"He wasn't part of a network, he did not receive instructions from anyone else, so there is no need to raise the terror threat alert level," the minister said, adding investigators had no precise information that any other attacks were likely.