Japan is mulling a new military buildup in its southernmost region with an eye on China, Japanese media has reported.

The Japanese government is considering deploying a surface-to-ship missile unit to the main Okinawa island in the hope of checking Chinese naval vessels that, Japan says, have repeatedly sailed through the Miyako Strait, the Asahi Shimbun said.

Japanese media said under international law there are no restrictions on Chinese naval vessels navigating in the open sea.

A battery of the most advanced Type 12 SSM, which has a range of about 200 kilometers, will be deployed on the main Okinawa island.

Together with the missile units on Miyako Island, the new deployments on Okinawa are believed to cover the entire sea area of the Miyako Strait, the Kyodo News reported.

Japan will add the upcoming developments into its new National Defense Program Guidelines, which will be worked out by the end of this year, and the Medium Term Defense Program.

The Kyodo News also reported that Japan is planning to launch an amphibious operations brigade at the end of March.

The 2,100-member unit, modeled after the US Marine Corps, will be stationed mainly in Sasebo in Southwestern Japan's Nagasaki prefecture.

Lyu Yaodong, a Japanese studies researcher at the Chinese Academy of Social Sciences, said the brigade will have combat capability and is obviously aimed at China's territorial and maritime sovereignty.

"The deployment of SSM and the brigade shows the (Prime Minister Shinzo) Abe administration's duplicity," Lyu said, adding that while Abe has stated many times his intention to use this year to improve China-Japan relations, the deployment actually targets China and threatens Chinese territorial security, which will undoubtedly damage the already-fragile bilateral relations.