The PLA daily, the Chinese military newspaper, on Sunday reported that the vessels were commissioned a day earlier in a ceremony held at an unspecified naval port, said to be in the South China Sea.
A Dongdiao-class vessel named Neptune was launched at the Hudong Zhonghua Shipbuilding Group yard in Shanghai in March 2014, IHS Jane's reported.
The Neptune is the third known Dongdiao-class vessel in service with the PLAN, according to IHS Jane's. The first, Beijixing, is based in the service's East Sea Fleet, while the second ship, Tianwangxing, is based in the South Sea Fleet.
According to IHS Jane's Fighting Ships, the 6,096-tonne boat has an overall length of 130 meters, an overall beam of 16.4 meters, and a hull draft of 6.5 meters. The ship has a top speed of 20 knots and can carry a crew of 250 and one medium helicopter. The Dongdiao-class is armed with one 37 millimeter and two 14.5 millimeter guns.
Two other ships inducted on the same day include a supply ship and a survey vessel, the PLA Daily reported.
The commissioning of the Neptune will further bolster the PLAN's sea-going intelligence collection and missile range instrumentation capabilities. Recent developments suggest that Beijing is stepping up its naval intelligence gathering operations amid a territorial dispute in the South China Sea.
Beijing claims sovereignty over nearly all of the South China Sea, but the Philippines, Brunei, Malaysia, Vietnam and Taiwan have overlapping claims.