BEIJING (REUTERS) - Japanese politicians are being provocative and are deceiving themselves about a territorial dispute, China's Foreign Ministry said on Monday, a day after Japan's prime minister said it was ready to be more assertive towards China.

Sino-Japanese ties have been overshadowed for years by what China says has been Japan's refusal to admit to atrocities committed by Japanese soldiers in China between 1931 and 1945. But relations have been further strained for months because of a dispute over tiny islands in the East China Sea, known as the Senkaku in Japan and the Diaoyu in China.

Japanese Prime Minister Shinzo Abe told his troops on Sunday that Japan would not tolerate the use of force to change the region's status quo, an expression used by Japanese politicians and security experts to refer to what they see as China's aggressive maritime expansion.

Chinese Foreign Ministry spokesman Hua Chunying, asked about Mr Abe's comments, said Japanese leaders had been repeatedly making "provocative" remarks. "This once again shows that Japanese politicians are deceiving themselves with their arrogance and guilty conscience," she told a daily news briefing.

Ties between Asia's two largest economies deteriorated sharply after Japan bought three of the disputed East China Sea islets from a private owner in September last year, sparking protests and boycotts of Japanese goods across China.

Ms Hua said Japan was to blame for upsetting the status quo over the islands.

"Japan's unilateral action on the Diaoyu islands from the start has been illegal and void. China will never accept it and will firmly oppose it. Everyone can see that it is Japan who has broken the status quo on the Diaoyu islands," she said.

Patrol ships from both countries have been shadowing each other near the islets, raising fears that an accidental collision or other unintended incident could develop into a clash.