Australia-Indonesia naval exercise begins

The Australian and Indonesian navies are starting four days of exercises to ensure smooth co-operation on the seas.

The Royal Australian Navy frigate HMAS Arunta and the RAN tanker HMAS Sirius arrived in Surabaya, East Java, on Monday, for exercise New Horizon.

The most important annual naval exercise of its kind between the two nations ensures their readiness to work together against mutual threats like transnational crime, human trafficking and terrorism.

HMAS Arunta's Commanding Officer Cameron Steil says regular exercises in refuelling, communication and live fire have built a continuous, positive working relationship.

"Navies are really good at building the diplomatic relationship between countries because we have a mutual understanding of the maritime domain as it is," he told AAP.

After the Java Sea exercises, HMAS Arunta and HMAS Sirius will head home to Australia after a two and a half month long tour of the Asian region.