MILAN (Reuters) - Milan prosecutors on Wednesday opened a preliminary investigation into alleged market manipulation after Mediaset's (MS.MI) top shareholder filed a complaint over Vivendi's (VIV.PA) stake-building in the Italian broadcaster, a judicial source told Reuters.
No individual or company is currently targeted by the investigation, which is against unknown persons, the source added.
Silvio Berlusconi's investment vehicle Fininvest, which owns 39.8 percent of Mediaset's voting rights, on Tuesday filed a complaint with prosecutors in Milan after the group chaired by Vincent Bollore said it could buy up to a fifth of the Milan-based TV company. [nI6N1E4002]
On Wednesday Vivendi said it had raised its stake in Mediaset to 20 percent from an initial 3 percent on Monday.
(This story has been corrected to change day of the week in first paragraph to Wednesday from Monday)
Reporting by Emilio Parodi, writing Giulia Segreti, editing by Silvia Aloisi, Steve Scherer and David Goodman