Chinese structures are pictured in disputed South China Sea.

China's military held joint sea and air patrols in the South China Sea on Saturday, a spokesperson for the People's Liberation Army's Southern Theater Command said.

Spokesperson Tian Junli said in a statement on Sunday that the Philippines has courted countries outside the region to organise "joint patrols" and "raised security risks" in the region.

"The theater command forces remain on high alert, resolutely safeguarding China's national sovereignty and maritime rights," he said, adding that "all military activities that seek to stir up trouble in the South China Sea or create flashpoints are fully under control."

The Philippine embassy in Beijing did not immediately respond to an emailed request for comment.

The Philippines and the United States conducted joint maritime drills in the South China Sea for a seventh time earlier this month.

Tensions have continued to run high between China and the Philippines over territorial disputes in the South China Sea, a conduit for more than $3 trillion of annual ship-borne commerce.

China claims almost the entire South China Sea, including parts claimed by Brunei, Indonesia, Malaysia, the Philippines and Vietnam.

In 2016 the Permanent Court of Arbitration in the Hague ruled that China's claims were not supported by international law, a decision that Beijing rejects.