FRIGHTENING footage spreading on social media appears to show a Hamas fighter holding a fake severed head after threatening "blood will flow" at the Paris Olympics.
But it's a bogus video produced by known Russian trolls, according to researchers from the Microsoft Threat Analysis Centre.
Footage, circulating on X and Telegram, shows a militant clad in black with his face wrapped up and his uniform sporting a Palestine flag.
He threatens in Arabic: "Rivers of blood will flow through the streets of Paris. The day is approaching, God willing."
He then raises a bloodied, severed head - too disturbing to show - while exclaiming "Allah is the greatest!"
The fake fighter warned of retaliation for France's support of Israel as the country welcomed Israeli athletes for the Games.
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But Microsoft researchers found it was produced by a Russian group known for spreading disinformation, reported.
Hamas official Izzat al-Risheq took to Telegram to deny the video came from the proscribed terror group currently at war with Israel, calling it a forgery.
Tech investigators said they matched details of the video with previous footage about the war in Ukraine.
The severed head, likely splashed in red paint, appeared to have come from a mannequin.
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Meanwhile, a Russian was arrested in France on suspicion of planning attacks during the Olympics.
French media reported a 40-year-old was detained on Sunday, with police probing whether he passed on "intelligence to a foreign power in order arouse hostilities in France".
The Russian plot is not believed to be terror-related.
But according to Le Parisien, a source close to the investigation dubbed the plot a "large-scale project that could've had "serious consequences".
The man is being kept in custody with a 30-year prison sentence reportedly on the cards.
It comes as an elite anti-terrorist unit has been deployed by France to protect the Israeli football team and fans.
The French Research and Intervention Brigade have been tasked with creating "ring of steel" at Israel's opening match against Mali at 8pm tonight.
A massive security operation is taking place all over Paris ahead of Friday night's opening ceremony.
It's set to be the most guarded games of all time, with an army of 60,000 cops and soldiers charged with protecting athletes and fans from evil.
Drones, helicopters and strict AI surveillance will support the biggest French deployment of troops since the Second World War.
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Organisers are preparing for all possibilities during the event amid of fears of terrorist attacks and chaotic protests.
Paris was rocked by recent election anarchy that led to tens of thousands of riot cops battling with opposing political supporters.