A fleet of four China Coast Guard (CCG) vessels patrolled territorial waters surrounding the Diaoyu Islands on Friday, according to a State Oceanic Administration statement.

The fleet was comprised of CCG 2151, 1126, 2146 and 2113, the statement said.

The CCG, which covers maritime law enforcement functions of four agencies responsible for fisheries administration, maritime surveillance, customs enforcement and border control, formally unveiled its board in July.

On Sept. 9, the administration said Chinese law-enforcement vessels had conducted 59 regular patrols around the Diaoyu Islands since September 2012, when Japan announced a plan to "purchase" the islands.

In the past year, Chinese ships have circled the islands at a minimum distance of 0.28 nautical miles.