"SHEN KUO" the China-flagged research vessel near Catanduanes. Photo Courtesy: Tactical Operations Wing Southern Luzon/AFP

MANILA -- The Armed Forces of the Philippines (AFP) said Sunday an unauthorized Chinese research vessel has been detected in the vicinity northeast of Viga, Catanduanes.

In a statement, the AFP said it first sighted the China-flagged vessel "SHEN KUO" on April 25 (Thursday), approximately 60.9 nautical miles east off Rapu-Rapu Island, Albay.

Map showing where the Chinese-flagged vessel was spotted in the northeast vicinity of Catanduanes on 27 April by TOWSOL personnel conducting maritime patrol. Photo courtesy of the AFP

The vessel was "lying-to in the area and had no personnel on the main deck," according to the latest reports from Tactical Operations Wing Southern Luzon, who conducted maritime patrol on April 27.

"Several attempts to contact the vessel through regular radio channels were unsuccessful, indicating a lack of responsiveness or willingness to engage," AFP said in its statement.

Meanwhile, AFP has tasked nearby vessels for "enhanced surveillance and reporting" as well as "coordinating with relevant agencies to address the unauthorized presence and investigate any illegal activities."