A joint Japan-US exercise in southwestern Japanese waters late this year near islands disputed with China is not necessarily targeting Beijing, Chinese scholars have said.

Japan's Yomiuri Shimbun reported on Thursday that Tokyo and Washington are planning a naval drill in Oita prefecture, near Okinawa and other southern islands, in December.

The news captured the attention of Chinese media as the two allies usually only stage their naval exercises east of Japan in the Pacific, which is closer to the Republic of Korea (ROK), which also has territorial disputes with Japan.

The concern was also due to the fact that the news came just one day after Tokyo said that territory disputed with China in the East China Sea is subject to the Japan-US security treaty, stressing that the allies would "respond together" to any attack there.

"We have not been notified by the United States that it has changed its stance" on the handling of the Diaoyu Islands, said Japanese foreign ministry press secretary Kazuo Kodama.

The Yomiuri Shimbun report said, without citing sources, that the exercise will be based on a scenario involving Japan recapturing an unnamed remote southwestern island from an enemy.

The US Navy's Seventh Fleet will join the exercise, said the newspaper. Japan is to send fighters and patrol planes, as well as 250 paratroopers from cargo planes guarded by F-15 fighters.

Neither the Chinese nor Japanese defense ministries responded to the report on Thursday.

Conflicts in the East China Sea have long existed between China and Japan.

Kyodo reported that in April a Chinese navy helicopter buzzed a Japanese Maritime Self-Defense Force destroyer in the East China Sea.

Beijing also protested to Tokyo through diplomatic channels over Japanese defense force surveillance flights over China's Chunxiao gas field in the East China Sea, Kyodo said. Beijing has proposed setting up a maritime emergency hotline with Tokyo to avoid accidental conflicts.

But Shen Shishun, from the China Institute of International Studies, said based on current information it is too early to decide whether the drill targets China.

"Both China and the ROK have territorial disputes with Japan in that region," he said. "We should not read too much into it so as to avoid misunderstanding."

Li Daguang, a military specialist with the University of National Defense, said the drill is "no more than a regular drill".

Still, Liu Jiangyong with Beijing-based Tsinghua University, said that for the US and Japan to hold such a large drill at a financially difficult time is strategically wrong and will offset efforts to maintain regional stability.

Seoul's Yonhap News Agency reported on Thursday that Seoul and Washington are considering reducing the scale of their joint naval exercises slated for early September to avoid raising unnecessary regional tensions. The two countries are scheduled to stage joint naval drills off the west coast of the Korean peninsula in September as the latest show of force aimed at preventing the Democratic People's Republic of Korea (DPRK) from waging further aggression.

The reported move comes after the DPRK and China protested the planned military maneuvers in the tense waters.

According to Yonhap, Seoul and Washington see the need to avoid discontent in the region, with Washington planning not to deploy its aircraft carrier USS George Washington for the latest drills.

In July, the ROK and the US held a massive four-day exercise in the Yellow Sea in response to the DPRK's alleged torpedo attack in March on a ROK warship, which killed 46 sailors. Pyongyang denies responsibility for the sinking.