China's biggest offshore oil producer, CNOOC Ltd , has been hit by another oil leak in north Chinese waters, state media reported on Saturday, following a June spill at a field run with ConocoPhillips that sparked wide concerns.

The latest spill broke out near the Jingzhou 9-3 field operated by a subsidiary of CNOOC in the Liaodong Bay off northeast China, Xinhua news agency reported.

CNOOC Ltd said on its website (www.cnoocltd.com) that "the oil spill was caused by the leak from a subsea connecting pipeline damaged by a work vessel during its operations."

The company said it had taken "effective measures to clean up the oil sheen as well as sent divers to survey the damaged subsea pipeline and seal the leaking source".

Production would be cut by about 1,600 barrels per day because of the shutdown, said CNOOC.

Maritime administrators also sent a ship to the area after a belt of oil floated to the surface near a platform on the field on Friday, said Xinhua. It did not describe the scale of the spill and said the ship was still investigating.