(Adds details on transaction and Friday acquisition) PARIS, Jan 25 (Reuters) - French media conglomerate Vivendi said on Monday it had raised its stake in Spanish rival Prisa, the owner of Spain’s influential El Pais newspaper and other media assets, to 9.9% from 7.6%. On Friday, Vivendi had announced it had bought the 7.6% stake, saying the move responded to the group’s strategy to become “a global leader in content, media and communications” and to extend its reach in the Spanish-language markets in Europe, Latin America and United States. Vivendi said it bought the stake hours after HSBC had agreed to sell a 7.89% stake in Prisa for 52 million euros ($63.3 million). Prisa, which is struggling with a huge debt pile, is controlled by activist fund Amber Capital which is led by French investor Joseph Oughourlian.