China on Tuesday reiterated its "indisputable sovereignty" over the Diaoyu Islands in response to four Japanese right-wing activists' landing on the islands.

"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 written statement released Tuesday afternoon.

The spokesman stressed that the Chinese government always holds a firm and unwavering determination in safeguarding its sovereignty over the islands.

According to Japanese media, four Japanese citizens, including municipal politicians, landed on the islands in the East China Sea on Tuesday morning. The group sailed to the uninhabited islets aboard a fishing boat and stayed there for more than two hours.