3 January 2012 Last updated at 08:10 ET

China protest at Japan disputed island visit

The dispute concerns eight small islands or rocks in the East China Sea

China says it has lodged an official protest after several Japanese politicians visited a group of disputed islands in the East China Sea.

Four Japanese citizens, including some local politicians, landed on the uninhabited islands on Tuesday and stayed for two hours, reports say.

The islands - known in Japan as Senkaku and in China as Diaoyu - are controlled by Japan, but claimed by China.

The area has rich fish stocks and possible oil deposits.

They are also close to key shipping lanes.

"I would like to reiterate that China has indisputable sovereignty over the Diaoyu Islands which have been an inherent part of China since ancient times," Chinese Foreign Ministry spokesman Hong Lei said in a statement.

Beijing added that it had "raised solemn representations and protest" with Tokyo over the visit.

Pro-China activists are also reported to have set sail for the islands in a journey expected to take two or three days, AFP news agency reports.

The islets, which are also claimed by Taiwan, have been a source of tension for decades.