President Bongbong Marcos said Tuesday the country will ask Beijing to explain its "more benign" account of an incident involving Chinese coastguard taking rocket debris from Filipino soldiers in disputed waters.

A senior Filipino navy official on Monday accused the Chinese coastguard of "forcefully" seizing parts of a rocket fairing that landed in the waters of the Spratly Islands in the hotly contested South China Sea.

Beijing insisted the handover took place after "friendly consultation".

"The report of the Philippine navy and the report from China did not match," Marcos told reporters.

"I have complete trust in our navy and if this is what they say happened, I can only believe that that is what happened."

Marcos said Manila would send a diplomatic note to Beijing asking "why is it that their account is so different and it's much more benign".

The South China Sea is a longstanding source of tensions between the two nations.

Beijing claims sovereignty over almost the entire sea and has ignored an international court ruling that its claims have no legal basis.

The Philippines, Vietnam, Malaysia, and Brunei have overlapping claims to parts of it.

Marcos's remarks came as US Vice President Kamala Harris wrapped up a visit to a Philippine island near the disputed sea in a show of support for the longtime US ally.

Harris said the United States "stands with the Philippines in the face of intimidation and coercion in the South China Sea."

Marcos has insisted he will not let China trample on the Philippines' maritime rights — in contrast to his predecessor Rodrigo Duterte who was reluctant to criticize the superpower.

In Sunday's incident, a Chinese coastguard vessel "blocked" a Filipino rubber boat towing an "unidentified floating object", Vice Admiral Alberto Carlos said Monday.