FILE PHOTO: The Vivendi logo at the company's headquarters in Paris, France, March 10, 2016. REUTERS/Charles Platiau/File Photo

PARIS (Reuters) - Police raided the headquarters of French media giant Vivendi on Thursday as part of an investigation into alleged market abuse involving its purchase of a stake in Italian TV group Mediaset, Vivendi said.

The offices of French bank Natixis in Paris were also being searched, an Italian source with direct knowledge of the matter said. A Natixis spokeswoman declined to comment.

Vivendi said Thursday’s raid was the result of an “unfounded and unjust complaint” by former Italian prime minister Silvio Berlusconi, whose holding company Fininvest lodged a criminal complaint last December alleging market manipulation against Vivendi.

Berlusconi and his family are the biggest shareholders in Mediaset through Fininvest, with a 39.5 percent stake and 41.1 percent of the voting rights, according to Mediaset. Vivendi comes second with a 28.8 percent stake and 29.9 percent of voting rights.

“Vivendi’s management reaffirms that it acquired its stake in Mediaset totally legally and transparently and remains absolutely confident in the conclusion of this disagreement,” the group said in a statement that confirmed the raid of its offices on Thursday.

The police raids follow a formal request sent by Milan prosecutors to French authorities several months ago.

Vivendi, led by tycoon Vincent Bollore, became Mediaset’s second largest shareholder in late 2016 when it bought a 20 percent stake in the Italian broadcaster.

Last December, when Vivendi acquired an 800 million-euro ($938 million) stake in Mediaset, two sources said Natixis was one of two banks mandated by the French group to carry out the purchase.