A Syrian refugee who stabbed six people, including four young children in Annecy, southeast France, was denied asylum in the country last month.
The suspect, who has been named as Abdalmasih H by French media, had his asylum request rejected because he has held refugee status in Sweden for the past 10 years.
French authorities rejected the request on 26 April but the suspect only learned of the decision on 4 June, French broadcaster BFMTV said.
The 31-year-old was arrested in connection with the attack at a lakeside park in which four children – two aged two, one aged three and a 22-month-old – suffered “life-threatening injuries”.
Foreign Secretary James Cleverly confirmed that one of the youngsters is British.
Two of the children were earlier reported as a brother and sister but BFMTV now report they are cousins.
The local prosecutor said another of the children is Dutch. However, Germany’s chancellor Olaf Scholz said they were German.
Two adult men were also injured, one of whom was injured with the knife and by a shot fired by police as they were making the arrest.
President Emmanuel Macron said those badly hurt in a park were “between life and death”.
Earlier, French Interior Minister Gerald Darmanin said the 31-year-old had entered France legally and was not known to security agencies.
The suspect also applied for asylum in Switzerland, Italy and France, which Mr Darmanin said he “didn’t need to do as he already had asylum in Sweden”.
He carried Swedish identity documents and a Swedish driving licence, a police spokesman said.
Prosecutor Line Bonnet-Mathis said the suspect’s motives were unknown but there was “no apparent terrorist motive” at this stage in the investigation.
There is no intelligence on the suspect and no psychiatric report, and he has no fixed abode, Ms Bonnet-Mathis said.
Mr Darmanin said he had certain “Christian religious insignia” on him during the incident.
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.
Video footage of the incident shows the man appears to shout “on name of Jesus Christ” as he waved his knife in the air, while two members of the public tried to apprehend him.
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 [prams], 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.
Former Liverpool footballer, Anthony Le Tallec, said he was jogging around Lake Annecy when he saw the incident unfold.
He commented: “I see that he’s [the attacker] heading straight for a group of elderly men and women.
“He attacks one grandpa, stabs him once, the cops can’t catch him, so I tell the cops, ‘shoot him’.
“Then they start shooting, they shoot at the person, right in front of me, and he falls to the ground.”
Prime Minister Elisabeth Borne said it was a “heinous, unspeakable act” and the whole country is in “shock”.
“Of course, all light will have to be shed. But today is the time for emotion,” she said during a press conference.
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.”
Speaking during a press conference with US President Joe Biden, Mr Sunak said he has been in touch with President Macron and is “ready to offer any assistance we can”.
In Paris, politicians interrupted a debate to hold a moment of silence for the victims.
Francois Astorg, the mayor of Annecy, urged people to avoid the Paquier area of the French alpine town and said his thoughts were with the victims and their families.