Top diplomat Wang Yi has warned his Philippine counterpart that Manila "must act with caution", the Foreign Ministry said, following a series of tense maritime confrontations in the South China Sea.

Wang said on a Wednesday call with Philippine Foreign Minister Enrique Manalo the two countries were "facing serious difficulties", blaming Manila for changing its policies, according to a readout.

"Wang Yi said China-Philippines relations are currently facing serious difficulties," it said.

"The root cause is that the Philippines has changed its longstanding policy stance, reneged on its own commitments, continued to provoke and stir trouble at sea, and undermined China's legal rights," it added.

"China-Philippines relations are at a crossroads. Faced with the choice of where to go, the Philippines must act with caution."

The Philippines had summoned China's envoy on December 11 and flagged the possibility of expelling him following the most tense clashes between the countries' vessels in years at flashpoint reefs.

Videos released by the Philippine Coast Guard showed Chinese ships blasting water cannon at Philippine boats during two separate resupply missions to fishermen at Huangyan Island and a tiny garrison at Ren’ai Jiao. (AFP)