Beijing slammed US Senator John McCain's remarks on Wednesday, in which he said the Diaoyu Islands are "Japanese territory", as irresponsible.

The former US presidential candidate told a Wednesday news conference in Tokyo that the Diaoyu Islands in the East China Sea are "Japanese territory", according to Kyodo News. McCain's statement is a deviation from the official US stance that it will not take a position on the sovereignty of the islands.

On Thursday, Chinese Foreign Ministry spokesman Hong Lei told China Daily in a written reply that, "The Diaoyu Islands are inherent territory of China and anyone's attempt to deny the fact will end up in vain."

"We urge the relevant US lawmaker to stop making irresponsible remarks and avoid further complicating relevant issues and regional situation," Hong said in the statement.

McCain also said nations who feel increasingly threatened by China's maritime presence "need to act in closer coordination with each other", as reported by Kyodo News.

Ties between China and Japan have been strained since last year after the Japanese government announced the purchase of three of the five islands from a private owner.