The state-run Chinese oil firm CNOOC reported an oil sheen was discovered in Bohai Bay near its Jinzhou 9-3 West oilfield.

The firm sent divers to seal the subsea pipeline, which it believes caused the leak after being damaged by a work vessel during operations.

CNOOC says it shut down operations at the field and immediately began to clean up the oil sheen on the sea surface. Initial estimates suggest the amount of leakage was about 0.38 cubic metres, roughly the same volume as two to three barrels of petroleum.