The militaries of the U.S. and Philippines have carried out joint drills in waters adjacent to the South China Sea claimed by Beijing, amid a rising number of incidents between China and the Philippines in the vital Southeast Asian waterway.

Participating in the maneuvers in the Sulu Sea this week were ships and aircraft from navies and coast guards, along with the U.S. Air Force, the U.S. 7th Fleet responsible for the Asia-Pacific said in a statement.

It said the drills included “exercises in maritime domain awareness, division tactics, maneuvering” and search and seizure.

There was no immediate comment from Beijing on the drills.

In a new national map released in 2003, the Chinese government demarcated its claim to virtually the entire South China Sea, with vague dash lines that drew protests and rejections from rival coastal governments, including Malaysia, Vietnam, Taiwan, Indonesia and the Philippines.

China has transformed seven disputed reefs into what are now missile-protected island bases, including Mischief Reef, which lies within the Philippines’ exclusive economic zone. The Sulu Sea lies inside that zone.

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China has ignored a 2016 international arbitration ruling that invalidated China’s extensive territorial claims based on historical grounds, and objects to activities by the U.S. military in the region — specifically those that challenge its island claims and threat to invade Taiwan, just north of the Sulu Sea.

The U.S. lays no claims in the waters, but has declared that freedom of navigation and overflight and the peaceful resolution of the conflicts are in its core national interests.

The U.S. also has a treaty obligating it to defend the Philippines if attacked and has been dispatching additional troops and weaponry to upgrade the island nation’s ability to defend itself.

China routinely harasses Philippine fishing boats in parts of the South China Sea, also within the Philippines’ exclusive economic zone, which extends 200 nautical miles (about 370 kilometers) from its coastline.