Beijing has called on Tokyo to explain what its intentions are in building a military radar station at the western end of its island chain, just 150 km from China's Diaoyu Islands.

Observers warned that the project, on which ground was broken on Saturday, would further bolster Japan's surveillance of the Chinese navy's efforts to safeguard its maritime interests.

Japanese Defense Minister Itsunori Onodera attended the ceremony to launch construction of the military project on Yonaguni Island, the westernmost Japanese land territory.

"It's very important to take a solid surveillance posture on remote islands," he was quoted as saying by Kyodo News.

Onodera suggested the military presence could be expanded to other islands in the seas southwest of mainland Japan.

A 150-strong Japanese Ground Self-Defense Force surveillance unit is due to be deployed on Yonaguni by the end of March 2016.

The military radar station, part of a longstanding plan to boost Japanese defense and surveillance, will be used to monitor ships and aircraft in the East China Sea, Kyodo reported.

Chinese Foreign Ministry spokeswoman Hua Chunying said on Friday that any move by Japan to strengthen its military presence in the region would raise concern among Asian countries due to historical reasons.

"We hope that Japan can learn from history, adhere to the path of peaceful development, respect and take seriously the legitimate security concerns of its Asian neighbors and do more to promote mutual trust and safeguard regional peace and stability," Hua said at the daily news conference.

Some Yonaguni residents are unhappy about the military project, fearing that the island could become a potential target.

Around 50 protesters tried to block Onodera from entering the construction site, Kyodo reported.

Lu Yaodong, a researcher of Japanese studies at the Chinese Academy of Social Sciences, said Tokyo's real intention in bolstering its military presence in its southwestern islands is to monitor China's military developments.

"Given the strategic location of Yonaguni Island, the deployment shows Japan's desire to hamper efforts by the Chinese navy to safeguard its maritime interests," Lu said.

Wang Xinsheng, a professor of Japanese studies at Peking University, said, "The lack of trust between Beijing and Tokyo has made the two neighbors' every move appear to be a threat to the other."

The groundbreaking ceremony on Yonaguni took place four days before US President Barack Obama is scheduled to land in Tokyo for a summit with Japanese Prime Minister Shinzo Abe, the first state visit to the country by a US president in 18 years.

The Japanese government proposed releasing a leaders' statement that says Washington must help Tokyo defend the Diaoyu Islands.

However, the US government was unwilling to specifically mention the islets by name because it did not want to unnecessarily irritate Beijing, Kyodo quoted a person familiar with Tokyo-Washington ties as saying on Wednesday.

"Reaffirming the US commitment to the Japan-US Security Treaty to pacify its ally is still an important topic during Obama's trip to Tokyo, but Washington is likely to pursue balance between China and Japan to avoid any deterioration of the current situation," Wang said.

In another development, a Japanese Cabinet minister visited the notorious war-linked Yasukuni Shrine on Sunday, ahead of the shrine's spring festival, which starts on Monday.

Keiji Furuya, chairman of Japan's National Public Safety Commission, said on his website that it is "natural for a Japanese citizen to pay tribute to the spirits of those who sacrificed their lives for the state".

The Yasukuni Shrine is considered a symbol of Japanese militarism during World War II because 14 convicted Class-A war criminals were enshrined there among Japanese war dead.

Earlier this month, Japanese Internal Affairs Minister Yoshitaka Shindo also prayed at Yasukuni. Abe, who visited the shrine in December, is reportedly not going to pay homage to the shrine during the spring festival to avoid provoking Washington in light of Obama's upcoming visit to Tokyo.

China and South Korea have urged Japan to face up to its past wartime history and maintain a correct attitude toward history, rather than attempt to whitewash its aggressive past.

Reuters and Xinhua contributed to this story.