“He wanted to attack everyone. I moved away and he lunged at an old man and woman and stabbed the old man,” former professional footballer Anthony Le Tallec, who was running in the park, told the local Dauphine Libere newspaper.

Another witness, named Malo, told the BFM television channel that the culprit attacked the children before the old man and was “shouting, but it wasn’t really comprehensible”.

Two of the children – believed to be aged around three – and an adult victim were in critical condition and fighting for their lives in hospital, a security source said.

Two children were foreign nationals, one Dutch and one British, the local prosecutor said on Thursday.

A police source said checks on the man, who was arrested at the scene, were ongoing, but he was unknown to French security services.

French President Emmanuel Macron called it an “attack of absolute cowardice”.

“The nation is shocked. Our thoughts are with [the victims] as well as their families and the emergency services,” he wrote on Twitter.

Annecy is a scenic town in the French Alps close to the border with Switzerland popular with tourists and home to one of the world’s top animation festivals, which starts Sunday.

Prime Minister Elisabeth Borne’s office announced she was travelling to the scene and MPs in the French parliament held a minute’s silence.

“We hope that the consequences of this extremely serious attack … will not send the country into mourning,” parliament speaker Yael Braun-Pivet told MPs as she interrupted a raucous debate about pension reform.

The motive and identity of the attacker are being investigated and the local prosecutor is expected to give further details at a press conference.

In 2012, a Franco-Algerian extremist called Mohamed Merah killed seven people during a shooting rampage in the southern city of Toulouse, with the murders of three children and a rabbi at a Jewish school sparking widespread outrage.

Most recently, the beheading of a teacher in broad daylight in 2020 near his school in a Paris suburb by a radicalised Chechen refugee led to shock and grief, as well as a national debate about the influence of radical Islam in deprived areas of the country.

Thursday’s attack is likely to spur greater scrutiny of immigration and asylum policy, with right-wing politicians immediately seizing on the suspected culprit’s identity as a refugee.

“The investigation will determine what happened, but it seems like the culprit has the same profile that you see often in these attacks,” the head of the right-wing Republicans party, Eric Ciotti, told reporters at parliament.

“We need to draw conclusions without being naive, with strength and with a clear mind.”

The leader of the alt-right National Rally party, Marine Le Pen, wrote that she had learned the news with “dread and horror”.

Additional reporting by Reuters