BEIJING - China on Wednesday demanded that Japan "immediately stop" unilateral marine surveys in the waters of the East China Sea, the Foreign Ministry said.

Ministry spokesman Hong Lei delivered the message at a daily news conference in response to a statement by Japanese Cabinet Secretary Osamu Fujimura earlier in the day.

On Tuesday, Hai Jian 66, a Chinese patrol vessel, radioed Japan Coast Guard's marine survey vessel Takuyo to stop operating in the disputed waters 140 km off Japan's Kumejima Island, according to Kyodo News Agency.

Tokyo later delivered an official protest to Beijing and vowed to continue similar operations.

Fujimura told reporters on Wednesday morning that the survey ship was operating in Japan's so-called exclusive economic zone "for marine research".

Fujimura said he "felt sorry" about China's repeated requests for a halt to the surveys, Japan's Jiji Press news agency said.

Beijing's stance on the East China Sea issue is consistent and clear, the spokesman said.

"China has required Japan to halt the related moves and avoid violating the due rights and interests of China."

Beijing hopes Tokyo can "sustain the stability of the East China Sea and the bigger picture of China-Japan ties", Hong said.

Japan's recent drive to beef up marine surveying in the disputed waters shows its urgency to secure more maritime interests, analysts said.

Tokyo's recent tough remarks show Japan's determination to lay claim to its so-called EEZ in disputed waters, said Zhou Yongsheng, a professor of Japanese studies at China Foreign Affairs University.

"Issues concerning sovereignty and core interests leave little room for concession from Beijing."

This year marks the 40th anniversary of the normalization of China-Japan diplomatic relations.

"We are not expecting the year of opportunities to turn into a year of challenges," Zhou said.

Tokyo recently disregarded Beijing's protests and conducted a series of unilateral surveys in the disputed waters of the East China Sea. A Chinese patrol ship had two encounters with survey ships of the Japanese Coast Guard this month.

The Chinese patrol vessel Hai Jian 66 on Feb 19 radioed Japan's Coast Guard survey ship Shoyo and called for a halt to its activities. Shoyo also claimed it was operating in Japan's so-called EEZ.

In another development, Japan's cabinet on Tuesday approved a set of bills to beef up Japan Coast Guard's law enforcement powers.

Under a bill to revise its Coast Guard Law, the Japanese government gave the coast guard the authority to arrest "illegal intruders" on remote "uninhabited islands".

The list of the "uninhabited islands" will be announced by officers of the Japan Coast Guard and the National Police Agency, and Kyodo said the list is expected to include China's Diaoyu Islands, over which China has indisputable sovereignty.

Another bill would revise the law banning foreign ships from mooring or moving within Japan's territorial waters without reasons.