A British man has appeared before a court in France after the bodies of his two children were found by police in his flat in Lyon.
The man, named by the Foreign Office as Julian Stevenson, is alleged to have cut the throats of his son and daughter.
Stephenson was driven into the court complex in Lyon hidden under a blanket. Reports say he is yet to be charged with premeditated murder.
"We are presently holding back from the charge of premeditated murder but this could always change in the light of (more) testimony," a prosecutor told the AFP news agency.
The children have been named in local reports as Mathew, 10, and Carla, five.
The father - who was said to be unemployed - had been living in France for some time, possibly around 10 years.
The 47-year-old and his French ex-wife, an assistant accountant, were said to have recently gone through a bitter divorce.
The children lived with her in the Isere region after she won custody.
They are believed to have been staying with their father for the first time at the weekend, who had visitation rights, but only in the presence of another person.
The children's mother is said to have been worried about the visit and had come to find them when she saw her ex-husband in the stairwell of the four-storey block of flats.
His clothes were reportedly stained with blood and she raised the alarm.
Reports suggested she had gone to his home after he failed to return the children following the visit.
Neighbours said they saw the man flee the scene on roller skates.
One man who lives in the same block described an earlier encounter with the couple.
He said: "I met his wife in the hall, crying. Her husband had thrown all her stuff out the window and she was picking it up, crying, because she was half-naked.
"What I can say is that he is a very aggressive man."
Stevenson is said to have admitted the killings "but did not go into details of the motive", prosecutors told AFP.
Neighbours said the couple had separated several years ago.
A Foreign Office spokesman said: "We are in touch with the French authorities and await the outcome of their investigation.
"We stand ready to provide consular assistance."