French police couple killed in attack claimed by Islamic State

A Frenchman who pledged allegiance to Islamic State stabbed a police commander to death outside his home and killed his partner, who also worked for the police, in an attack the government denounced as "an abject act of terrorism".

Larossi Abballa, 25, also took the couple's three-year-old son hostage in Monday night's attack. The boy was found unharmed but in a state of shock after police commandos stormed the house and killed the attacker.

Born in France of Moroccan origin, Abballa was jailed in 2013 for helping Islamist militants go to Pakistan and had been under security service surveillance, including wiretaps, at the time of the attack, Paris prosecutor Francois Molins said.

The attacker told police negotiators during the siege he had answered an appeal by Iraq-based Islamic State chief Abu Bakr al-Baghdadi "to kill infidels at home with their families", Molins told a news conference.

"The killer said he was a practicing Muslim, was observing Ramadan and, that three weeks ago, he had pledged allegiance to ... Abu Bakr al-Baghdadi," Molins said.

Police found a bloodied knife at the scene along with a list of other potential targets including rap musicians, journalists and police officers, the prosecutor said.

The killings came as France, which has been under a state of emergency since Islamic State gunmen and bombers killed 130 people in Paris last November, was on high security alert for the Euro 2016 soccer tournament, which began last Friday.

In a video posted on social networks, Abballa linked the attack to the soccer championship, saying: "The Euros will be a graveyard."

The video had been removed from Facebook on Tuesday. Michelle Gilbert, a Paris-based spokeswoman for Facebook, said the company's guidelines forbade hate messages and aimed to remove such content swiftly from the website once alerted.