French prosecutors on Monday launched a preliminary investigation into a top-flight footballer on suspicion of glorifying terrorism after he reposted an allegedly anti-Semitic message on social media relating to the Israel-Hamas conflict.

Youcef Atal, an Algerian international who plays for Ligue 1 club Nice, is suspected of sharing a video from a Palestinian preacher on Instagram purportedly calling for violence against Jewish people.

Football officials, politicians, a Jewish group and the mayor of Nice have all condemned the message, which Atal deleted before apologising. 

AFP has not been able to independently verify the content of the original post. 

France, which has large Jewish and Muslim populations, ramped up security after Hamas launched a massive attack on Israel on October 7.

And officials put the country on high alert for potential attacks after a teacher was stabbed to death on Friday by a former pupil, in what politicians have said was Islamist terrorism. 

The Nice prosecutor's office confirmed in a statement it was investigating Atal after being notified by local politicians. 

The prosecutors said police would also assess if the post amounted to incitement to religious hatred or violence.

The French Football Federation (FFF) said on Sunday its ethics committee would investigate the player, with FFF president Philippe Diallo denouncing the contents of the post.

Atal responded to the criticism on Sunday, telling his Instagram followers he would "never support a message of hate", without explaining why he had shared the video. 

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