Banco Bilbao Vizcaya Argentaria SA, Spain's second-biggest bank, agreed to pay about 1 billion euros ($1.51 billion) to boost its investment in China's State-owned CITIC Group to strengthen its foothold in Asia.

BBVA exercised an option to buy an additional 4.93 percent in China CITIC Bank to bring its holding in the lender to 15 percent, the Bilbao, Spain-based company said in a filing to regulators. BBVA paid HK$6.45 (83 cents) per share for the stake, the bank said.

The bank agreed three years ago to buy stakes in CITIC Group companies for 989 million euros, acquiring an initial 5-percent stake in CITIC Bank, and 15 percent of CITIC International Financial Holdings Ltd as it targets China to diversify revenue.