A Frenchman once convicted of recruiting jihadi fighters stabbed a police commander to death outside his suburban Paris home, recording the attack and posting it on Facebook Live, French officials say.

The commander’s partner and the attacker were found dead inside the home after a three-hour stand-off with police.

The couple’s three-year-old was in the house in Magnanville, about 55km west of Paris, but was unharmed. A police official said that at one point in the video the attacker puzzled over what to do with the child.

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The Islamic State’s Amaq news agency cited an unnamed source as saying an IS fighter carried out the attack late on Monday. While the extremist group has not officially claimed responsibility, French President Francois Hollande said it was “incontestably a terrorist act” and that France faces a threat “of a very large scale”.

Two people close to the attacker, identified as 25-year-old Larossi Abbala, were detained, authorities said Tuesday. They gave no details about them.

France has been on particularly high alert as it hosts Europe’s top sporting event, the month-long European Championship soccer tournament, and is still under a state of emergency after the November IS attacks in Paris that killed 130 people.

Hollande held an emergency security meeting Tuesday.

“France is not the only country concerned (by the terrorist threat), as we have seen, again, in the United States, in Orlando,” he said.

Abbala was from the nearby suburb of Mantes-la-Jolie and was sentenced in 2013 to three years in prison for recruiting fighters for jihad in Pakistan, according to two police officials. The officials spoke on condition of anonymity because they were not authorised to be publicly named discussing investigations.

Two other security officials who also spoke on condition of anonymity said Abbala recorded a video during the knife attack. One official said the assailant posted the video on Facebook Live, the social media site’s live feed.

A Facebook profile bearing the name Larossi Abbala – which vanished from the internet early Tuesday – showed a photo of a smiling, bearded man. Two recent posts featured videos critical of Israel and Saudi Arabia. The last publicly available post was a mock-up of the European Championship logo, highlighting what the poster said were masonic and occult symbols.

“Some will say we see evil everywhere!” Abbala said in a message posted about 18 hours before the attack.

On Tuesday, Interior Minister Bernard Cazeneuve visited the police station in the suburb of Les Mureaux where 42-year-old Jean-Baptiste Salvaing worked. Police did not identify his partner but said she was an administrator for police in Mantes-La-Jolie.

Cazeneuve said more than 100 people seen as potential threats have been arrested in France this year, including in recent weeks.