France on Friday launched a criminal investigation into claims by World Cup winner Paul Pogba that he is the victim of a multi-million euro blackmail plot by gangsters involving his brother, the Paris prosecutor said.

Two investigating magistrates have been appointed to lead the probe, prosecutor Laure Beccuau said in a statement.

Based on the findings of a preliminary investigation launched last month it will examine allegations – for now against persons unknown – including blackmail by an armed gang, kidnapping and membership of a criminal conspiracy, she said, confirming a weekend statement from a judicial source.

Pogba's allegations came after his brother Mathias published a bizarre video online – in four languages (French, Italian, English and Spanish) – promising "great revelations" about the Juventus star.

According to two sources close to the Pogba family contacted by AFP, large sums of money are being demanded from Paul Pogba if he wants to avoid the dissemination of allegedly compromising videos.

France Info reported that Paul Pogba told investigators he had been threatened by "childhood friends and two hooded men armed with assault rifles".

They are demanding 13 million euros ($13 million) from him for "services provided", it said.

Pogba explained to investigators that his blackmailers wanted to discredit him by claiming he asked a marabout (holy man) to cast a spell on the Paris Saint-Germain and France star Kylian Mbappé, which Pogba denies.

The investigation is handled jointly by the French police's anti-gang and central crime units.

Several people, including Pogba's mother, have already been interviewed by police, a judiciary source told AFP.

(AFP)