Indonesia and the United States have kicked off their annual joint drills, with a record number of other countries participating or observing.

"Super Garuda Shield" is one of the biggest multilateral exercises in the Indo-Pacific. It aims to boost security cooperation to keep the region free and open.

Indonesia and the US have staged the drills annually since 2007. They were expanded in 2022 to involve troops from other countries. This year more than 20 nations have sent forces.

On Monday, troops gathered for the opening ceremony at Surabaya naval base in East Java.

Maj. Gen. Widyargo Ikoputra of the Indonesian Air Force said, "The Super Garuda Shield joint exercises this year are to build mutual trust in the military field and to strengthen bilateral and multilateral military relations."

Maj. Gen. Joseph Harris, commander of the Hawaii Air National Guard, said, "Our collaboration during events like this demonstrates our resolve and commitment as like-minded partners for a free and open Indo-Pacific."

This year's drills, held through September 6, will focus on cybersecurity and training to retake captured islands.

Southeast Asian countries, including Indonesia, lie in the center of the Indo-Pacific, where key sea-lanes are located. China's muscle-flexing in the waters has been causing concern.