By Ruth Bender 

PARIS--French conglomerate Bolloré Monday said it raised its stake in Vivendi SA, tightening investor Vincent Bolloré's grip on the French media group.

Groupe Bolloré, controlled by Mr. Bolloré, said it raised its stake in Vivendi to 8.2% from 5.2% after acquiring 40.5 million new shares for a total of EUR852 million.

Mr. Bolloré took over the chairmanship of Vivendi In June last year with his 5% stake.

Mr. Bolloré has pledged to make Vivendi's units work more closely together after the group refashioned itself into a media company, selling assets in videogames and telecoms over the past few years.

Vivendi's two fully-owned assets today are French pay TV Canal Plus and U.S.-based music company Universal Music Group.

Bolloré increasing its stake "testifies to the confidence that the Bolloré group has in the capacity to develop Vivendi" the group said in a statement.

Write to Ruth Bender at Ruth.Bender@wsj.com

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