France on Saturday said it will deploy 7,000 soldiers after declaring a top-level alert following the fatal stabbing of a teacher by a man of Chechen origin, who also severely wounded three others at a school, France 24 reports.
The attack took place in the northeastern town of Arras, home to large Jewish and Muslim populations.
Police arrested the suspected attacker, Mohammed Moguchkov, who had cried the Arabic phrase "Allahu Akbar!" (God is greatest), according to the preliminary elements of the investigation.
Authorities have suggested a probable link to the ongoing violence in the Middle East, with President Emmanuel Macron denouncing the incident as an act of "Islamist terror".
The deployment of the soldiers from Operation Sentinelle will be completed by Monday evening, according to the Élysée presidential palace.
Sentinelle is a French military operation with 10,000 soldiers and 4,700 police and gendarmes deployed since the aftermath of the January 2015 attacks to protect parts of the country deemed sensitive from terrorism.
"This school was struck by the barbarity of Islamist terrorism," Macron said after visiting the school, adding that the victim had "probably saved many lives" with his courage in blocking the attacker.
Macron said another attempted attack in another region had been foiled by security forces.
According to the interior ministry, the president was referring to the arrest of a "radicalised" man who was arrested leaving a prayer hall in the Yvelines département (administrative unit) near Paris for carrying a prohibited weapon.
Interior Minister Gérald Darmanin later said there was "probably a link between what's happening in the Middle East and this incident" in Arras.
France upped its alert level to the highest position following a crunch security meeting chaired by Macron on Friday, the prime minister's office told AFP.
A total of 10 people have been put into custody, a police source told AFP on Saturday.
In addition to the suspected attacker, several members of his family are being held following the stabbing on Friday, the source said. Two Belarusians were among those in custody, another police source said.
The national anti-terrorism prosecutor announced that it has opened an investigation.
Moguchkov, who is in his 20s, is from Russia's mainly Muslim southern Caucasus region of Chechnya. He was already on a French national register known as "Fiche S" as a potential security threat, a police source told AFP, and under electronic and physical surveillance by France's domestic intelligence agency, the DGSI.
