MILAN, May 31 (Reuters) - The board of Generali unanimously approved the 1.17- billion-euro offer for Cattolica , two sources close to the matter said on Monday.

Italy's biggest insurer Generali said on Monday it would launch a buyout offer for smaller Italian rival to further cement its domestic leadership.

Some Italian shareholders in Generali, such as Italian businessman Francesco Gaetano Caltagirone and eyewear magnate Leonardo Del Vecchio, have criticised some of the insurer's strategic moves in the past year, including the purchase of 24% of Cattolica last October, sources have previously said.

(Reporting by Gianluca Semeraro; editing by Giulia Segreti)