Chinese coastguard ships are frequently spotted by rival fleets deep in the South China Sea.

Malaysia complained publicly of interference by the Chinese coastguard.

It was escorted by two Chinese coastguard ships.

The most recent incursion, just this week, included a geological survey vessel and two Chinese coastguard ships.

Andy Li was among 12 people caught by Chinese coastguards on 23 August.

Chinese coastguard and navy vessels trespassed in Malaysia's waters despite being turned away by its navy, it said.

The standoff began earlier this month, with Chinese coastguard vessels supporting the survey ship confronted by Vietnamese patrol ships.

The Chinese coastguard vessels sailed into the 12-nautical-mile territorial waters off one of the Senkaku islands on Sunday afternoon.

In the distance, a Chinese coastguard ship guarded the mouth of the reef, preventing the larger boats from entering.

In March last year, a Chinese coastguard vessel rammed a Chinese fishing vessel to free it following its seizure by Indonesian authorities.

Dozens of Vietnamese and Chinese coastguard and fishing vessels have repeatedly squared off around the rig, resulting in a number of rammings and collisions.

Sunday's intrusion was the first since 29 December 2013 when three Chinese coastguard ships entered the zone and stayed for about three hours.