Australia and key partners India, Japan and the United States have completed the second phase of Exercise Malabar 2021, held in the Indian Ocean.

Anzac-class frigate HMAS Ballarat and replenishment oiler HMAS Sirius, with ships and aircraft from the other participating nations, engaged in complex multi-domain training in the Bay of Bengal from October 11-14.

This followed the first phase of the exercise, held in August near Guam.

Commander of the Australian Fleet, Rear Admiral Mark Hammond, said the exercise further strengthened Australia's ties with partners.

"Exercise Malabar built our collective ability to meet shared challenges in pursuit of an open, inclusive and resilient Indo-Pacific," Rear Admiral Hammond said.

"The Royal Australian Navy has enjoyed multiple opportunities to work with India, Japan and the United States this year, including the first phase of Exercise Malabar 2021, as well as other navy-to-navy activities.

"Each time we work together, we refine our shared mariner skills, improve our interoperability and further strengthen our professional ties."

Ballarat and Sirius are home-ported at Fleet Base West in Western Australia and have both spent significant time deployed throughout the Indo-Pacific working with regional partners.