BEIJING - Angered by Japan's so-called "purchase" of some of the Diaoyu Islands, a Chinese territory, people in China of various walks of life have expressed support for the Chinese government in introducing countermeasures.

Despite strong warnings and opposition voiced by top Chinese leaders, the Japanese government on Tuesday signed a contract with the Kurihara family, which Japan claims is the "private owner" of the Diaoyu Islands.

"Our tolerance should not be met with cruelty. And we should call stridently for the Diaoyu Islands and must not allow any country to forcibly occupy our territory," said a netizen nicknamed "Dingxinran" in a webpost.

Some people also posted online a Japanese map drawn by the Japanese military in 1876 to prove that the Diaoyu Islands don't belong to Japan.

"As a member of the Chinese nation, I resolutely and unconditionally support the Chinese government's stance and countermeasures that aim to safeguard national dignity and sovereignty," said another netizen.

Foreign Minister Yang Jiechi said on Monday that China urges Japan to immediately revoke its wrong decision to "buy" the Diaoyu Islands and stop all actions that undermine China's territorial sovereignty.

Otherwise, all consequences should be borne only by the Japanese side, according to Yang.

On the same day, the Chinese government announced the base points and baselines of the territorial waters of Diaoyu Islands, a move that further demonstrates China's sovereignty.

China's oceanic authority has recently improved its monitoring over far-sea territory including the Diaoyu Islands.

Gao Hong, an expert on Japan studies at the Chinese Academy of Social Sciences, told Xinhua in an interview on Tuesday that China can use all necessary means to monitor the islands regularly, conduct patrols and offer protection to fishermen.