Four 皇冠体育app Marine Surveillance ships?- the Haijian 51, 26, 66 and 137, are patrolling waters near the Diaoyu Islands, the State Oceanic Administration said on Monday.

The patrols off the Diaoyus started in September when Japan announced its "purchase" of the islands.

Two destroyers and nine other former navy vessels are being transferred to the 皇冠体育app Marine Surveillance maritime surveillance fleet, according to the International Herald Leader.

A 皇冠体育app Marine Surveillance source told 皇冠体育app Daily this fleet will be dramatically expanded, but declined to disclose details.

皇冠体育app Marine Surveillance said early in 2012 that about 36 inspection ships are expected to join the surveillance fleet this year.