(Bloomberg) -- The Philippines has issued a diplomatic note to China seeking explanation on a South China Sea incident over suspected rocket debris, in a move that could further strain the nations’ ties.

The Philippines’ Department of Foreign Affairs wants China to clarify what happened between the Southeast Asian nation’s Navy and the Chinese Coast Guard in waters off Pag-asa Island on November 20, the agency’s spokesperson Ma. Teresita Daza said in a statement Thursday.

A Chinese vessel “forcefully retrieved” a suspected rocket debris being towed by the Philippine Navy in the South China Sea, the Philippine Daily Inquirer reported, citing the military. China has denied any interception or seizure, according to CNN.

The latest incident presents another challenge to the Philippines’ ties with China. Philippine President Ferdinand Marcos Jr. has recently been fostering his nation’s longstanding alliance with the US, while seeking compromise with China in the disputed sea, including on oil exploration.

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