Fatal stabbing of policeman in front of son outside Paris deemed 'terrorist attack'
The killing of two police officers in a knife attack outside Paris was "incontestably a terrorist act", French President Francois Hollande has said.
Speaking at the Organisation for Economic Co-operation and Development in the capital, Mr Hollande said France was facing a terror threat "of a very large scale".
"France is not the only country concerned (by the terrorist threat), as we have seen, again, in the United States, in Orlando," he said.
Earlier, after emergency talks with the president, Interior Minister Bernard Cazeneuve warned that France, Europe and the West remain under a high threat of extremist violence, adding that more than 100 people seen as potential threats have been arrested in France this year, including in recent weeks.
France has been on particularly high alert as it hosts Europe's top sporting event, the month-long European Championship football tournament, and is still under a state of emergency after deadly Islamic State attacks in Paris on November 13 in which 130 people were killed.
French anti-terrorism prosecutors are investigating Monday night's attack on an off-duty police chief and his partner.
The Islamic State's Amaq news agency cited an unnamed source as saying an IS fighter carried out the attack, but the extremist jihadist group has not officially claimed responsibility.
France, like other countries in Europe, has seen a series of stabbings aimed at police officers or soldiers and carried out by Muslim radicals. IS has encouraged its supporters to stage such attacks.
French officials identified the suspect as Larossi Abbala, a 25-year-old who had a past terrorism conviction for recruiting fighters for jihad in Pakistan.
They said Abbala was from the western Paris suburb of Mantes-la-Jolie and was jailed in 2013 for three years, including six months suspended for association with a terrorist enterprise.
The off-duty police commander was attacked outside his home in Magnanville, about 35 miles (55km) west of Paris. The knifeman then went into the property and elite police commandos laid siege to the residence, eventually storming it after a three-hour stand-off.
Interior ministry spokesman Pierre-Henry Brandet said the woman, the commander's companion and a fellow police worker, was found dead. The police couple's three-year-old son was unharmed.
Officials said the attacker was killed by police when they stormed the residence.
"The toll is a heavy one," Mr Brandet told reporters, his voice heavy with emotion.
"This commander, this police officer, was killed by the individual ... (and) we discovered the body of a woman. The assailant, the criminal, was killed. Thankfully, a little boy was saved. He was in the house. He's safe and sound. He was saved by police officers."
The Paris prosecutor's office said anti-terrorism investigators had been brought in to the case given the target, the method behind the attack, and what the attacker said to police during the ensuing stand-off.
The office did not elaborate, but French media, some of them citing unnamed neighbours, reported that the attacker was heard shouting "Allahu Akbar" - Arabic for "God is Great" - during the attack.
French prosecutor Vincent Lesclous - who said he knew the murdered police commander - told reporters the boy was found "shocked but unharmed".