Beijing - Beijing on Tuesday rejected Japanese protests against two Chinese ships entering the waters around a group of disputed islands in the East China Sea.

The Diaoyu Islands have been part of China since "ancient times" Liu Jinachao, a Foreign Ministry spokesman, was quoted as saying by the official Xinhua news agency.

"The usual cruising of the Chinese ships within Chinese seas is irreproachable," he said.

The islands, a source of bilateral tension for many years, are called Diaoyu in China and Senkaku in Japan.

Japan has held the islands since China9s defeat in the Sino-Japanese War in 1895, but they are also claimed by China and Taiwan.

The latest incident is the first of its kind since 2004.

Japan's government on Monday lodged a formal protest against the incursion of the two Chinese maritime survey ships and demanded their withdrawal.

"Such activity is extremely regrettable and we demand immediate withdrawal," Chief Cabinet Secretary Takeo Kawamura said. (dpa)