One man was killed and two other people seriously injured in a knife attack by an unidentified assailant in the Paris suburb of Villejuif on Friday.

Police shot dead the assailant, who has not been identified. The motive is still unknown. The attacker apparently stabbed people at random in the Hautes-Bruyères park, which was packed with families and children during the school holidays. He stabbed two people before he entered the park.

The man who died was an elderly local man who tried to defend his wife, who was stabbed in the neck and is described as being in critical condition in hospital.

Police cordoned off the area as they checked for possible accomplices. Anti-terrorist prosecutors have gone to the scene to assess whether the motive was terrorism.

Loïc Travers, a police union spokesman, said: “No one can be sure at this stage whether this was a terrorist act.”

Witnesses told Le Parisien newspaper that the attacker shouted “Allahu Akhbar” as he lunged at passers-by.

Yves Lefebvre, another police union spokesman, said the offficers had opened fire on the attacker because they feared he might be wearing a suicide belt.

Police used a robot to examine his body for explosives but none were found. The assailant, who has not been named, was psychologically troubled, according to local sources. He was known to be in the habit of walking barefoot in the park.