The Philippine navy on Monday accused the Chinese coastguard of "forcefully" seizing a floating object that its troops had just recovered in disputed South China Sea waters.

A senior Filipino navy official made the allegation on the eve of a visit by US Vice President Kamala Harris to a nearby Philippine island aimed at boosting ties amid China's growing regional clout.

A Chinese coastguard vessel on Sunday "blocked" a Filipino rubber boat towing an "unidentified floating object" toward Philippine-garrisoned Thitu island in the Spratly group, Vice Admiral Alberto Carlos said.

The coast guard vessel then deployed an inflatable boat team which "forcefully retrieved said floating object by cutting the towing line attached to the (Filipino) rubber boat", he said in a statement.

The object "looks similar" to floating debris that resembled Chinese rocket fairings which were recovered this month from the island of Busuanga, north of Palawan, military spokeswoman Major Cherryl Tindog told reporters.

The object, which the Filipinos first saw 732 meters (800 yards) west of Thitu in the morning, was then taken to the Chinese coastguard vessel as the Filipino troops returned to their station, Carlos said.

No Filipino soldiers were injured in the incident, he added.

The Chinese embassy in Manila did not immediately reply to a request for comment.

The Philippine foreign department said it was "aware of the incident and awaits the detailed reports from maritime law enforcement agencies".

The reported incident came hours before the US vice president began a three-day visit.

After meeting Philippine President Ferdinand Marcos Jr. on Monday, Harris is due to visit the western Philippine island of Palawan, the closest major landmass to the Spratlys, on Tuesday.

China claims sovereignty over almost the entire South China Sea, a resource-rich waterway through which trillions of dollars worth of ship-borne trade passes every year.