MANILA (BLOOMBERG) - The Philippines will protest against China's opening of a maritime rescue centre in the South China Sea, Foreign Affairs Secretary Teodoro Locsin said, just days after Philippine President Rodrigo Duterte's spokesman said the nation should be grateful for the move.

Mr Locsin said he supports Supreme Court Justice Antonio Carpio's position that the Philippines must contest China's construction of the rescue centre on Fiery Cross Reef, which Xinhua reported on Jan 29.

Mr Carpio was part of the Philippine delegation which won a 2016 ruling that China's efforts to assert control over the South China Sea exceeded the law.

Under Chinese President Xi Jinping, China has built a web of artificial islands with runways and lighthouses to exert influence in the South China Sea, raising the ire of countries including the Philippines, Malaysia and Vietnam, who also lay claim to the area.

"We will" protest if the reports turn out to be true, Mr Locsin said on Twitter. "I however preferred engaging them openly on the floor of the UN General Assembly."

He said his department is awaiting National Security Adviser Hermogenes Esperon's assessment, as the government cannot rely on media accounts.

Mr Duterte's spokesman Salvador Panelo last week said the Philippines should be "thankful" to China, saying a rescue centre can help everybody.