Two of the children and an adult are in a life-threatening condition, police have said.

Foreign Secretary James Cleverly confirmed that one of the youngsters is British.

A brother and sister, aged two and three, are the ones who have been seriously injured and are in intensive care, broadcaster BFMTV said.

Another of the children is Dutch.

The English child is said to be two; another of the injured is a German child aged 22 months, the channel said.

It added that two adults had been injured, both men, one of whom is 78.

French President Emmanuel Macron said those badly hurt in a park were "between life and death".

A man who spoke to broadcaster BFMTV said he saw first aiders working on "little bodies, three or four years old, perhaps".

A witness who gave his name as Ferdinand told BFMTV: "He (the attacker) jumped (in the playground), started shouting and then went towards the strollers, repeatedly hitting the little ones with a knife."

"Mothers were crying, everybody was running," said George, who owns a nearby restaurant.

A further witness said he saw the attacker assault an elderly man, jumping on him and stabbing him repeatedly. He said he yelled at police to act.

"It's a place where babysitters and parents take young children to play, and the atmosphere is fantastic," said Yohan, who works at an ice cream parlour just opposite the park.

Interior Minister Gerald Darmanin said a suspect had been arrested "thanks to the swift intervention of police".

The perpetrator is a 31-year-old Syrian asylum seeker who carried Swedish identity documents and a Swedish driving license, a police spokesman said.

He entered France legally and was not known to security agencies.

Line Bonnet-Mathis, the prosecutor of Annecy, said a police firearm was used during his detention, and he was slightly injured.

He has had refugee status in Sweden for the last 10 years, she said.

There is no intelligence on him and no psychiatric report, and he has no fixed abode, Ms Bonnet-Mathis said.

He is married to a Swedish woman and they have a three-year-old child who was born in Sweden, BFMTV reported.

The couple separated eight months ago and his wife has apparently not heard from him for four months.

He and his wife were studying together to be nurses, BFMTV said.

His motivation is unclear, a source told the Reuters news agency.

Video footage shows two members of the public trying to apprehend him.

BFMTV showed footage of several policemen overpowering an individual in the park.

France attack: What we know about stabbing in Annecy playground

Mr Macron said it was an "absolutely cowardly attack in a park" and the "nation is in shock".

There is "nothing more abominable than to attack children", French national assembly speaker Yael Braun-Pivet said.

British Prime Minister Rishi Sunak said: "The UK and France have always stood together against acts of violence, and we do so again today."

Francois Astorg, the mayor of Annecy, said he was at the scene and will be speaking at lunchtime.

He urged people to avoid the Paquier area of the French alpine town and said his thoughts were with the victims and their families.

In Paris, politicians interrupted a debate to hold a moment of silence for the victims, BFMTV said.