The Armed Forces of the Philippines said on Saturday that it had staged naval and air drills with counterparts from the United States, Australia and New Zealand from Thursday to Friday in the disputed South China Sea.

It’s the 12th such military drills that the Philippines says it has staged with other friendly nations since last year to protect its sovereign rights in the disputed waters.

The military drills included an anti-submarine warfare simulation, replenishment and fuelling at sea, fly-bys and communication exercises.

They also involved a Philippine navy guided missile frigate and surveillance aircraft, another frigate from Australia with an MH-60R Seahawk helicopter, an auxiliary navy ship from New Zealand and a U.S. Navy guided missile destroyer, the USS Fitzgerald, the Philippines military said.

The exercises underscore “the enduring commitment of the four nations to strengthen maritime cooperation, enhance interoperability and uphold peace and stability under a rules-based international order in the Indo-Pacific region,” Philippine military spokesperson Col. Xeres Trinidad said in a statement.

He did not provide other details, including where the joint exercises were staged in the disputed waters.