China on Tuesday launched the Japanese and English versions of a digital museum aimed at demonstrating the country's claims to the Japanese-administered Senkaku Islands in the East China Sea, the official Xinhua News Agency reported.

By displaying "legal and historical proofs" that the islets belong to China, the website "helps the international community further understand the indisputable fact" that Diaoyu Islands are China's inherent territory," Xinhua said.

File photo taken in September 2012 shows the Senkaku Islands in the East China Sea. (Kyodo)

China calls the uninhabited islets in the East China Sea Diaoyu. The museum had been viewable only in Chinese since it was officially opened in October last year.

Sino-Japanese relations have often been frayed by the territorial issue, although the two Asian powers have been trying to improve their ties for the past years by effectively shelving it.

China has frequently sent official ships to waters around the islands in a bid to push its claims to them, while Washington and Tokyo have agreed that the islets fall under the scope of a Japan-U.S. security treaty.

On Monday, meanwhile, the Chinese Ministry of Natural Resources issued a landform survey report on the islands, saying it was designed to obtain data to manage resources and protect the ecological environment of the islets.

The Japanese Foreign Ministry has lodged a protest against China over the survey through diplomatic channels, criticizing it for being based on the assumption that the Asian neighbor has claims to the islands, according to sources familiar with bilateral relations.

Rapidly building artificial islets with military infrastructure, Beijing also claims sovereignty over the almost entire South China Sea -- a strategic waterway through which more than one-third of global trade passes.

Chinese President Xi Jinping late last week instructed his People's Liberation Army to strengthen exercises to seize islands in the nearby waters, sources close to the matter said.

The move is apparently a warning against the United States and other Western democratic nations that have been stepping up their involvement in the South China Sea and the Taiwan Strait, foreign affairs experts say.