A gunman on a police watchlist for contacts with Islamist extremists launched a brazen suspected terror attack in Belgium, shooting dead two female police officers with their own weapons before killing a bystander.The bloodshed in the gritty eastern industrial city of Liege began at around 10:30 (08:30 GMT) on Tuesday when the attacker, armed with a knife, repeatedly stabbed the two officers before using their own firearms to kill them, prosecutors said.Federal prosecutors said they had launched a terror investigation into the incident.Amateur footage aired by Belgium's state broadcaster showed the gunman shouting "Allahu Akbar" ("God is greatest") as he walked through the streets during the rampage.In another video, a short and intense burst of gunfire is audible, after which the man lies on the ground."Armed with a knife, the suspect followed and attacked two police officers, and used their own firearms to kill them," prosecutor Philippe Dulieu told a news conference."He continued on foot, attacking a parked vehicle where he opened fire on a 22-year-old man in the passenger seat. The young man died."He then continued and entered the Leonie de Waha school. He took a woman working there as hostage. Police intervened, he came out firing on the police officers, wounding several before he was killed."'Radicalised in prison'Belgium remains on high alert after a string of attacks including twin suicide bombings in Brussels in 2016 claimed by the Islamic State (ISIS) group.A source close to the investigation told AFP that the gunman was on a special police watchlist because of his contacts with radical Islamists.The source named the attacker as Benjamin Herman, born in 1982, saying he had past convictions for robbery, violence and drug dealing.Herman was "already on the run" after committing another murder on Monday night in the town of On, in southern Belgium, the source said, though local prosecutors said they have not yet established a link with the Liege incident.He was reported by Belgian broadcaster RTBF to have been released from prison on Monday."He is suspected of having been radicalised (in prison)... He has been reported or presumed to be belonging to the entourage of an Islamist recruiter," the source said on condition of anonymity.Liege police chief Christian Beaupere said it was "clear that the assassin's objective was to attack the police". He added that one of the four officers wounded in the attack had suffered a serious leg injury.Liege, a major city in Western Europe's former industrial heartland, was the scene of another bloody shootout in 2011.In that attack, a former convict armed with grenades and an automatic rifle killed six people and wounded more than 120.'Cowardly violence'Prime Minister Charles Michel denounced what he called the "cowardly and blind violence" of Tuesday's attack."All our support for the victims and their loved ones. We are following the situation with the security services and the crisis centre," Michel tweeted.There was support from other European countries, with French President Emmanuel Macron condemning the incident as a "terrible attack" and expressing the "solidarity of the French people".British Prime Minister Theresa May said the UK "stands resolute with our Belgian allies against terror".A major security cordon was set up around the area, while panicked parents came to collect their children from the school complex.The governor of Liege province said all the children and staff were safe and unhurt."All the children are fine, those of the primary and kindergarten saw nothing, they were evacuated through the back of the school," Julie Fernandez, mother of a seven-year-old at the school, told AFP."They were cared for by staff and psychologists and high school students were cared for in a nearby park," added Fernandez, who is also an MP.Terror alertBelgium has been on high alert since authorities in January 2015 smashed a terror cell in the town of Verviers that was planning an attack on police.The cell also had links to Abdelhamid Abaaoud, the mastermind of the November 2015 ISIS attacks on Paris that killed 130 people.Belgium further raised its terror alert level after the Paris attack and placed the capital Brussels on lockdown for a week.The country was then hit itself by ISIS suicide attacks on Brussels airport and a metro station, which killed 32 people in March 2016.In August that same year, a machete-wielding man shouting "Allahu Akbar" attacked two female police officers in the industrial town of Charleroi before being shot dead.The country's law enforcement agencies and intelligence services came under intense scrutiny for apparently missing a series of leads after the Paris attacks that could have led to the Brussels bombers.