Japan's prime minister reached out to the leaders of China and South Korea at an Asia-Pacific summit, officials said Tuesday, but Beijing said that more than handshakes were needed to ease deep tensions among Asia's biggest economies.

Shinzo Abe managed a brief encounter with Chinese President Xi Jinping on Monday and with South Korean President Park Geun-Hye on Tuesday, as all three attended group meetings of the Asia-Pacific Economic Cooperation forum in Indonesia.

"I understand that he shook hands with the two leaders," Japanese Chief Cabinet Secretary Yoshihide Suga told reporters in Tokyo.

"I think it's good that the leaders see each other repeatedly and exchange greetings," he said, after Abe staged similar encounters with Xi and Park at a Group of 20 summit in Russia last month.

But while Japanese media afforded heavy coverage to the encounters, playing up Abe's warm smile as he conferred with Park in one APEC session, Beijing's reading was more frosty.

"I think the Japanese side should stop putting the cart before the horse," foreign ministry spokeswoman Hua Chunying told reporters, insisting that Japan should first accept the reality that the nations are locked in a territorial dispute in the East China Sea.

Japan maintains there is nothing to discuss because the islands -- called Senkaku by Tokyo and Diaoyu by Beijing -- are indisputably Japanese and that China should move on to bigger matters between the world's second- and third-largest economies.

"Without making any concrete effort, the Japanese side is only playing up these kinds of reports," Hua said, urging Tokyo "to remove the obstacles to the improvement of bilateral relations".

There was no immediate comment from South Korea on the encounters, which fell short of Abe's desire for full meetings with his neighbours' leaders.

"I want to seize on an opportune time to exchange views" with them in Bali, Abe said in Tokyo on Sunday before leaving for the two-day APEC gathering, which ended on Tuesday.

"I want to send a message that the door of dialogue is always open."

Abe has not held formal talks with the Chinese and South Korean leaders since taking office last December. Tokyo's ties with its neighbours have been strained by territorial disputes and the legacy of Japan's 20th century wartime aggression.

Abe's brief handshake with Xi at the G20 in Saint Petersburg represented the first encounter between leaders of the two countries since relations took a nosedive in 2012 over the ownership of the uninhabited islands in the East China Sea, a row that has led to warnings of a possible armed confrontation.

The last trilateral meeting among China, Japan and South Korea was in May last year in Beijing, when the trio's predecessors gathered.

Relations between Japan and South Korea had appeared to warm in the first half of 2012.

But they turned icy in August with then South Korean president Lee Myung-Bak's sudden visit to Seoul-controlled islands that lie in waters between the two countries.

Tetsuro Kato, professor emeritus at Tokyo's Hitotsubashi University, said the fact that all Abe had to show from his meetings was a few handshakes was "not a normal situation", but that he could not see it changing in the near future, especially with China.

"This situation will continue as long as Japan sticks to the position that the disputed islands are an 'integral part of Japan'," he told AFP.

China's reasserted its claim to the Senkaku/Diaoyu islands after Japan nationalised some of the isles in September 2012. Rival official ships have patrolled the area ever since, while warships and fighter planes have made occasional forays, leading some to fear that full-scale conflict could erupt.

Tokyo insists its move was intended to pre-empt a bid by nationalists to buy the islands, believing that that would have been much more inflammatory.

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