Photo/IllutrationThe Indian aircraft carrier Vikramaditya (Provided by the Indian Navy)

Japan deployed its largest contingent yet to a joint naval exercise also involving the United States and India in the Bay of Bengal that is aimed at keeping maritime advances by China in check.

The Malabar maneuvers in the Indian Ocean are primarily designed to monitor Chinese submarine activity in the vital sea lane.

"Maintaining the stability of the Indian and Pacific oceans is an important national interest of the three nations," said Hiroshi Yamamura, vice chief of staff of the Maritime Self-Defense Force. "Our involvement is aimed at deepening the relationship between the three nations."

A ceremony was held July 10 at Chennai Port to mark the start of the joint training exercise, which continues until July 17.

This year, Japan sent the helicopter carrier Izumo, the MSDF's largest vessel. A record 700 or so MSDF members are taking part, according to an MSDF source.

A key feature of the Izumo deployment is that it is able to handle nine helicopters simultaneously to maintain surveillance over submarines.

A high-ranking Defense Ministry official said, "The Izumo was the most appropriate vessel to demonstrate Japan's seriousness about the exercise."

The first Malabar exercise in 1992 was between the United States and India. It has been held alternatively in the Indian and Pacific oceans.

Japan first took part in 2007 and has been participating on an annual basis since 2014.

Under an agreement reached in 2016 for Japan to take part on a continual basis, the exercise has from this year become an official joint training exercise involving the three nations.

In addition to simulating anti-submarine warfare, other training elements this year will include refueling ships at sea.

Prime Minister Shinzo Abe touched upon the Malabar exercise during talks July 7 on the sidelines of the Group of 20 summit in Germany with Indian Prime Minister Narendra Modi, calling it "a symbol of defense cooperation between Japan and India."

India sent its lone aircraft carrier, the Vikramaditya, while the U.S. Navy dispatched the flattop USS Nimitz.

In total, the three nations will deploy 16 ships, two submarines and dozens of aircraft for the exercise.

The focus on anti-submarine warfare arises from recent Chinese activity. In 2014, a Chinese submarine made a port call in Sri Lanka, and one the following year in Pakistan, demonstrating China's efforts to strengthen relations with coastal nations in the region.

Beijing has also provided support to nations with Indian Ocean coastlines that are beefing up their harbor and port facilities.

According to the Indian media, Chinese submarines were spotted this month prowling in the Indian Ocean.

(This article was written by Ryo Aibara in Tokyo and Takeshi Narabe in Chennai, India.)