UPDATE 1-Vivendi further raises stake in Telecom Italia to 23.8 pct

(Adds details on mandatory bid threshold, background)

MILAN, March 1 (Reuters) - French media group Vivendi has raised its stake in Telecom Italia to 23.8 percent, further strengthening its position as the top shareholder in the Italian phone group, according to a regulatory filing.

This brings Vivendi’s stake to just below a 25 percent threshold that under Italian regulations would force it to launch a mandatory bid for Telecom Italia. Sources close to the matter have said Vivendi is likely to stay below the 25 percent level.

A filing with the U.S. Securities and Exchange Commission, dated March 1, said Vivendi bought on the market 135 million shares between Feb. 22 and Feb. 29.

Vivendi, controlled by tycoon Vincent Bollore, previously had 22.8 percent of the Italian company, having topped up its holding between Feb. 16 and Feb. 19.

Vivendi received an 8.2 percent stake in Telecom Italia in June last year from Telefonica as part payment for selling its Brazilian broadband telecoms group GVT to Telefonica Brasil .

Since then, it has gradually increased its stake in the Italian company, fuelling speculation about its intentions given that it now has four representatives on Telecom Italia’s board.

Back in October, when it reached 20 percent, Vivendi said the move confirmed its intention to develop its activities in southern Europe, in a statement analysts said could be a prelude to a deal involving Spain’s Telefonica.

The stake increase comes as speculation mounts in the Italian press that Vivendi may be interested in the pay-TV arm of Mediaset, Italy’s biggest private broadcaster, which is controlled by former prime minister Silvio Berlusconi.

A source close to Vivendi, which has four representatives on Telecom Italia’s board, has said however the group was too busy working on other projects to start talks with Mediaset.

Vivendi declined to comment. (Reporting by Silvia Aloisi, additional reporting by Gwénaëlle Barzic in Paris; editing by Susan Thomas)