SHANGHAI (Reuters) - State-run CNOOC <0883.HK>, China's top offshore oil producer, has issued a tender to invite foreign firms to bid for oil and gas blocks in the East and South China Sea, according to a statement on the company website.

CNOOC said it would offer 25 offshore blocks for foreign participation this year, including 17 in the South China Sea and three in the East China Sea.

(Reporting by Fayen Wong and Beijing newsroom; Editing by Alan Raybould)