QINGDAO - An oil spill was discovered in North China's Bohai Sea Friday evening and is being assessed for damage, maritime authorities said.

The Jinzhou 9-3 oil-drilling rig is seen in Liaodong Bay, in North China's Bohai Sea, Oct 15, 2011. [Photo/Xinhua]

The Tianjin branch of the China National Offshore Oil Corp said it discovered the spill after an oil slick was spotted near the Jinzhou 9-3 oilfield, which is located in Liaodong Bay, on Friday.

The source of the oil is an underwater pipe that was damaged by the anchors of ships passing through the bay, the company said in in a report.

The State Oceanic Administration (SOA) has initiated a level-three emergency response to the spill and has dispatched a plane and a monitoring vessel to assess any possible damage.

The spill comes after the government's pledge to inspect offshore petroleum drilling and exploration businesses to prevent future oil spills.

The pledge was a response to a severe oil spill that occurred in Bohai Bay in June, wreaking havoc on local tourism and aquatic farming.

The June spill originated from a platform belonging to ConocoPhillips China, a subsidiary of US-based oil giant ConocoPhillips.

The company has been criticized for its failure to clean up the spill in accordance with a deadline imposed by the Chinese government.

The Bohai Sea is the innermost gulf of the Yellow Sea and comprises Laizhou Bay, Liaodong Bay and Bohai Bay.