China Marine Surveillance vessels expelled two Vietnamese ships from waters near the Xisha Islands during a routine patrol on Wednesday morning, Xinhua News Agency reported.
The Vietnamese ships were first detected at about 7 am, illegally fishing in Chinese waters.
At 10 am, the Haijian 262 and Haijian 263 expelled the two vessels from waters off the Xisha Islands and recorded their illegal behavior.
Since 2007, China has carried out routine patrols in its territorial waters to safeguard its sovereignty, according to China Marine Surveillance.
The State Oceanic Administration said three surveillance ships are patrolling waters off the Diaoyu Islands in the East China Sea, declaring the Chinese government's stance on the islands after Japanese ships illegally entering these waters on Tuesday.