A China Marine Surveillance (CMS) detachment accomplished an airborne and seaborne patrol of the Xisha Islands in the South China Sea ahead of schedule on Thursday.

A China Marine Surveillance (CMS) detachment approaches the port of Sanya after finishing an airborne and seaborne patrol of the Xisha Islands in the South China Sea on Thursday. [Photo/Xinhua]

Surveillance ships and helicopters arrived at the port of Sanya in south China's Hainan Province at 4:15 p.m..

Three CMS ships -- the Haijian 83, Haijian 262 and Haijian 263 -- and helicopter Haijian B-7103 took part in the operation, which began on Sunday and was scheduled to patrol the northern waters of Xisha for nine days.

The detachment has surveyed 29 islands and their surrounding waters, with law enforcement personnel on the ships landing on 10 of them, According to Zhang Weijian, the on-site director of the mission.

Zhang said the the detachment has accomplished regular patrol and observation missions, including assessing maritime space management, marine ecology and island protection.

"The major problem we found during the patrol is that some fishermen set temporary settlements on uninhabited islands, and their waste management need to be improved," according to Zhang.

China has created an environmental protection plan for the Xisha Islands so as to protect their ecology, the mission director added.

This is the first time that Chinese maritime helicopters and ships have carried out a joint patrol around the Xisha Islands since Sansha City, which administers the three islands groups of Xisha, Zhongsha and Nansha, was officially set up in July last year.