A 29-year-old extremist suspected of killing two people near a Christmas market in Strasbourg shouted “God is great” as he opened fire.

A massive manhunt is under way for Cherif Chekatt after the shooting which left 12 people injured and another brain dead.

Prosecutor Remy Heitz said witnesses heard the gunman shout Allahu Akbar – God is Great in Arabic – during chaotic scenes in the city in eastern France.

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Cherif Chekatt is being hunted by French police (AP)

One of those killed was named as Thai national Anupong Suebsamarn, 45, who had been on holiday in France with his wife.

They had reportedly planned to be in Paris but the yellow vest protests in the capital caused them to change their itinerary and go to Strasbourg instead.

A young Italian radio journalist who was in the city to cover a session of the European Parliament was critically injured. Antonio Megalizzi, who works for the Europhonica radio consortium linked to universities, was shot in the head.

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People remember the victims the night after the shooting in Strasbourg (Christophe Ena/AP)

Mr Heitz said the gunman was shot in the arm during an exchange of fire with soldiers before taking a taxi to another part of the city. He said Chekatt was armed with a handgun and a knife.

He also said police found a grenade, a rifle and four knives during a search on Tuesday morning of Chekatt’s house in an investigation over an attempted murder.

Police union officials said that Chekatt had a long criminal record for offences including armed robbery and that he was monitored as a suspected religious radical by the French intelligence services.

A judicial official said that Chekatt’s father and two brothers were among four people taken into custody as part of the investigation.

He said other members of Cherkatt’s family are known for radical views.

Interior minister Christophe Castaner said 720 officers are hunting for the gunman and the French government has increased its security alert system Vigipirate to its highest level.

Mr Castaner said: “The government has decided to move the security level to “Emergency Attack” with stricter controls at the borders, and the implementation of reinforced controls on all the Christmas markets that are taking place in France to avoid the risk of copycat attacks.”

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A French soldier patrols next to Notre-Dame cathedral of Strasbourg (Jean Francois Badias/AP)

Witnesses described shots and screams after the gunman opened fire in a city that is home to the European Parliament and considers itself a capital of Europe — and promotes itself as the “capital of Christmas”.

Senior Interior Ministry official Laurent Nunez said the suspect had been radicalised in prison and had been monitored by French intelligence services since his release in late 2015, because of his suspected religious extremism.

At Chekatt’s apartment, in an outer neighbourhood of Strasbourg, the lock of the door was broken at his apartment and police were guarding the building.

A neighbour, who asked not to be named because the gunman was still at large, said he was rarely home. She said she last saw him on Monday from her window, which looks out on a common hallway, and he was with another man.

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French police officers check cars at the French-German border (Christophe Ena/AP)

Young men from the apartment block said they knew him as someone who seemed destabilised by his time in prison. “You can just tell,” said one.

The suspected attacker’s more than two dozen convictions also included crimes in Germany and Switzerland, according to court documents.

The attack is a new blow to France, which saw a wave of Islamic extremist killings in 2015 and 2016.

While authorities urged people in the area to stay inside after Tuesday’s attack, Strasbourg Mayor Roland Ries told BFM television Wednesday that “life must go on” so that the city does not cede to a “terrorist who is trying to disrupt our way of life.”