The Chinese armed forces are capable of "safeguarding" the country's territory, a military spokesman was quoted as saying by state media on Thursday, amid a territorial dispute with Japan.

Geng Yansheng, a spokesman for the Ministry of Defence, also repeated Beijing's claim to a chain of disputed islands in the East China Sea known in China as Diaoyu and in Japan as Senkaku.

"It is undisputed that the Diaoyu Islands are an indispensable part of China's territory," Geng was quoted as saying by the Xinhua news agency.

"In the meantime, China's armed forces are capable of safeguarding the country's territory as well as its maritime rights and interests," he said.

Tensions between the neighbours flared earlier this month after pro-Beijing activists landed on one of the disputed islands, which are controlled by Japan. They were arrested by Japanese authorities and deported.

About a dozen Japanese nationalists raised their country's flags on the island days later.

Thousands of Chinese citizens in more than 20 cities have protested after the incidents. Japanese businesses, restaurants and cars were targeted in some cities.

On Monday, the car of the Japanese ambassador to China was targeted in Beijing when an unidentified man ripped the national flag off the vehicle.

Japan's foreign minister Tuesday said it was time to address relations with China.

US Secretary of State Hillary Clinton, who is due in Beijing for talks with Chinese officials next week, is expected to raise maritime disputes in the region.

China and other Asian countries also have rival claims to disputed territory in the resource-rich South China Sea.