Takaichi suggested last month that Japan would intervene militarily in any Chinese attack on Taiwan, the self-ruled island that Beijing claims as its own and which it has not ruled out seizing by force.

J-15 jets from China's Liaoning aircraft carrier on Saturday twice locked radar on Japanese aircraft in international waters near Okinawa, according to Japan. No damage or injury was caused.

Fighter jets use their radar for fire control to identify targets as well as for search and rescue operations.

China's navy said Tokyo's claim was "completely inconsistent with the facts" and told Japan to "immediately stop slandering and smearing".

Vice Foreign Minister Takehiro Funakoshi summoned ambassador Wu Jianghao on Sunday and "made a strong protest that such dangerous acts are extremely regrettable".

Funakoshi "strongly urged the Government of China to ensure that similar actions do not recur," the Japanese foreign ministry said late Sunday.

Takaichi said on Sunday that Japan would "respond calmly and resolutely.

"While closely monitoring the movements of the Chinese military in the sea and airspace surrounding our country, we will ensure thorough vigilance and surveillance activities in the surrounding sea and airspace," she said.

Beijing's foreign ministry said it rejected that protest, and had lodged its own counter-protest, according to state news agency Xinhua.

A foreign ministry spokesperson, cited by Xinhua, urged Japan to "immediately stop its dangerous moves of harassing China's normal military exercise and training".

Last week Japanese and Chinese vessels engaged in a fresh standoff around disputed islands administered by Japan in the East China Sea that have long been a flashpoint.

Japan's coast guard said two Chinese coast guard patrol ships entered Japan's territorial waters around the Senkaku Islands, known as the Diaoyu in China, and demanded they leave.

China's coast guard said a Japanese fishing vessel "illegally entered China's territorial waters" and that its vessels took "necessary control measures and made warnings to drive it away".

- Rare earths -

The comments on November 7 about Taiwan by Takaichi, seen before she became premier in October as a China hawk, have enraged Beijing.

China has urged its citizens to avoid Japan -- they are the biggest source of tourists -- and cultural events involving Japanese performers and movies have been hit.

Aside from reportedly renewing a ban on Japanese seafood imports, China has however so far stopped short of imposing more serious economic measures such as curbing exports of rare earth metals.

But the Yomiuri Shimbun daily reported on Sunday that China's export permit procedures for rare earths -- key ingredients for smartphones and electric vehicles -- to Japanese companies were taking longer than usual.