Indonesian President Joko Widodo and Japanese Prime Minister Shinzo Abe Sunday reaffirmed their commitment to cooperate on maritime security and deepen defence ties, as both nations feud with China over sea territory.

Abe -- in Indonesia on a regional tour that has taken in Australia and the Philippines and will include Vietnam -- said their two island nations gave maritime cooperation the "highest priority".

"Japan will actively encourage cooperation on maritime security and encourage the development of the remote islands of Indonesia," he said through a translator at the presidential palace in Bogor.

Last month Tokyo and Jakarta unveiled an agreement aimed in part at strengthening Indonesia's ability to defend its vast marine borders.

Indonesia has no argument with China over ownership of reefs or islets in the disputed South China Sea. But Beijing's expansive claims overlap with Indonesia's exclusive economic zone -- waters where a state has the right to exploit resources -- around the Natuna islands.

Indonesia has vowed to protect its sovereignty from intrusions by fishing vessels, and has blown up foreign boats in a show of force, including some from China.

Japan, which has a territorial row with China over disputed islands in the East China Sea, has worked to strengthen ties with members of the Association of Southeast Asian Nations such as Indonesia.

It has repeatedly stressed that maritime disputes should be addressed according to law.

The defence and foreign ministers of Japan and Indonesia will meet this year to discuss deepening "cooperation in the fields of defence and security", Abe added.

Widodo said Japanese investment in Indonesia had nearly doubled from 2015 to almost $5 billion last year. The two leaders discussed opportunities centred on large infrastructure projects including a medium-speed rail line and key port.

Widodo is trying to spur growth in Southeast Asia's largest economy by increasing infrastructure spending, particularly on the country's creaking roads, ports and railways.

Japan has won bids to construct Indonesia's largest coal-fired power plant and a mass rapid transit system for Jakarta. But it lost a lucrative contract to China to build the country's first high-speed rail network.