BEIJING - The surveillance ships in China's latest patrol activity returned to base on Saturday after they inspected the oil fields in waters of the East China Sea and the waters close to the Diaoyu Islands in two days.

Along with other four surveillance ships, the Haijian 50 and Haijian 66, the flagship patrol boats of China, arrived early Saturday in the area near the "Chunxiao" and "Pinghu" gas fields to conduct an inspection tour, following their patrol in the waters close to the Diaoyu Islands on Friday, according to the State Oceanic Administration (SOA).

Lately, the fastest Haijian 66 successfully kept the unauthorized Japanese survey ships out of the East China Sea waters under Chinese jurisdiction, according to the SOA.

To safeguard the oceanic tapping order and the safety of China's maritime facilities is a significant task of the regular patrol conducted by China Marine Surveillance (CMS), a maritime law enforcement agency under the SOA, said Liu Zhendong, commander of the patrol team.

The CMS began routine patrol and law enforcement missions in the sea areas within China's territory on July 20, 2006, while It conducted patrol near the Diaoyu Islands and adjacent islets on December 8, 2008.