The Chinese Embassy in Manila said Friday it has filed a diplomatic protest against a Philippine Coast Guard spokesman over a social media post that included cartoonish images of President Xi Jinping.

Coast Guard spokesman Jay Tarriela and an embassy official had been trading barbs since last week over issues concerning the disputed South China Sea.

The crucial waterway, which Beijing claims historic rights to despite an international ruling that its assertion has no legal basis, has been the site of repeated clashes between Chinese and Philippine vessels.

Tarriela's Facebook post on Wednesday included a photo of him giving a speech, with a background featuring a compilation of comical images of Xi under the banner "Why China remains to be bully?"

On Friday, the embassy slammed the post for "attacking and smearing Chinese leaders" in a statement it released.

The move "constitutes a serious violation of China's political dignity", the embassy said adding that it is a "blatant political provocation, which has crossed the red line".

The embassy expressed "strong indignation" to the presidential palace, foreign affairs department and coast guard demanding an explanation for Tarriela's "malicious provocations".

In response, Tarriela Friday branded the protest "an attempt to deflect from the core issue: China's repeated aggressive and illegal actions in the West Philippine Sea," using the Filipino term for the waters immediately west of the country.

"If the Chinese Embassy objects to images or expressions that highlight these violations -- often through legitimate public discourse or even satire -- it only underscores discomfort with the truth being exposed," Tarriela said, calling the response an "effort to intimidate".

Manila's presidential palace and Department of Foreign Affairs have yet to answer AFP's request for comment.