A terrorist linked with Isis has stabbed to death a French Police chief and his wife and took their child hostage in their home in Magnanville, near Paris, before being killed by police.
French media say the attacker had been sentenced in 2013 for involvement with jihadist groups with links to Pakistan.
Unnamed sources identified him as 25-year-old Larossi Abballa, who lived in nearby Mantes-La-Jolie and was convicted for “criminal association with the aim of preparing terrorist acts”.
He was sentenced to a three-year term, with six months suspended, they said.
Islamic State’s Amaq news agency said an IS “fighter” carried out the attack.
If that is confirmed, it would be the first militant attack in France since a state of emergency was imposed following last November’s attacks which left 130 dead in Paris.
And it happens as the country is in high alert as it hosts the Euro football championship, which started on Friday.
Speaking after a cabinet meeting held by President Francois Hollande, Mr Cazeneuve said more than 100 people seen as potential threats have been arrested in France this year, including in recent weeks.