China has sent two patrol ships to the East China Sea islands to "assert its sovereignty" over a group of disputed islands in the East China Sea.
According to a Xinhua report, two navy surveillance ships have reached the waters of the islands known as Senkaku in Japan and Diaoyu in China and would "take actions pending the development of the situation."
The development followed Tokyo's confirmation that it had purchased part of the disputed islands from private owners. The Japanese government has bought three out of the five islands from the Kurihara family, which had owned them since 1972.
"This should cause no problem for Japan's ties with other countries and regions," said Japan's Chief Cabinet Secretary Osamu Fujimura.
"We have absolutely no desire for any repercussions as far as Japan-China relations are concerned. It is important that we avoid misunderstanding and unforeseen problems."
China has maintained that the islands are an integral part of its territory. Earlier, China had summoned the Japanese ambassador to lodge its strong protest over the decision to purchase the islands.
China's premier Wen Jiabao said his country would never cede what it perceives at its sovereignty.
"We have been monitoring the developments of the situation closely and will take necessary measures to uphold China's territorial sovereignty," said China's foreign ministry spokesman Hong Lei.
The islands are located south of Okinawa and north of Taiwan and are believed to be rich in natural resources and fishing areas. It is controlled by Japan, but China and Taiwan also raise claim to the territory, which lies near major shipping lanes.
The latest flare-up in the territorial row began in August with Chinese and Japanese nationals trying to storm the islands to stake claim to the territory in the name of their respective countries.
Japanese authorities arrested and deported a group of Hong Kong-based activists who brought flags of the People's Republic of China (mainland) and of the Republic of China (Taiwan) onto the main island in the Senkaku/Diaoyu group. Japanese activists followed up by swimming to the island and waving their own national flag.
The incident followed a group of Japanese activists entering the island and waving Japanese flags. Later, two Chinese men were arrested for tearing the Japanese flag from a car carrying the Japanese envoy in Beijing.