MADRID (Reuters) - Spain’s Banco Santander said on Friday it has increased by 10.4% its offer to buy out the 8.3% stake it does not already own in its Mexican unit, a move seeking to strengthen its grip on its Latin American businesses. Santander said on Friday it was offering Banco Santander Mexico’s minority shareholders 26.5 Mexican pesos ($1.30) per share, up from 24 Mexican pesos previously. The offer, which the lender expects to launch on November 3, would be worth more than 600 million euros ($700 million). Santander has expanded in emerging economies where it hopes to register a faster growth than in Spain and Britain, its core markets in Europe. ($1 = 20.4515 Mexican pesos) Reporting by Jesús Aguado; editing by Inti Landauro