China and South Korea on Wednesday pressed Japan to face up to its wartime past, as festering territorial disputes flared and Asia marked the anniversary of Tokyo's World War II surrender.

Both countries demanded Japan do more to atone for the brutal expansionism of the 20th century, while in Tokyo cabinet ministers paid tribute to fallen Japanese, including top war criminals, at a controversial shrine.

Beijing said the key issue was "whether Japan can really look in the mirror of history, heeding its lessons, holding hands with Asian people to face the future".

"The power is in the hands of Japan itself," it added. "We hope Japan can keep its promise to deal with and reflect on its invasion history and take concrete measures to safeguard China-Japan relations."

In Seoul, President Lee Myung-Bak, whose visit to disputed islands last week sent relations with Tokyo into virtual freefall, said Japan had to make amends for the sexual slavery it forced on women in its former colony.

"It was a breach of women's rights committed during wartime as well as a violation of universal human rights and historic justice. We urge the Japanese government to take responsible measures in this regard," Lee said.

"Chain links tangled in the history of Korea-Japan relations are hampering the common march toward a better tomorrow in the Northeast Asian region, as well as bilateral ties," Lee said.

The demands came as Japanese police arrested 14 people, some of whom had landed on on an island claimed by both Beijing and Tokyo.

The group had sailed from Hong Kong to the archipelago, known as Senkaku in Japan and Diaoyu in China, with the intention of planting a Chinese flag.

Japan summoned the Chinese ambassador in response.

Their action came just days after South Korea's Lee landed on another set of disputed islands, kicking back into life a long-slumbering row with Japan, which this week morphed into a warning that Japan's emperor must apologise if he ever wanted to visit.

Tokyo rounded on Lee, who had previously been viewed as a pragmatist with whom it could deal.

Foreign Minister Koichiro Gemba said his comments on the emperor -- a respected figurehead in Japan -- were "extremely regrettable" and "difficult to comprehend".

As Seoul celebrated Liberation Day, around 500 South Koreans, including two former comfort women, rallied outside the Japanese embassy in Seoul.

It was their 1,035th weekly protest over the issue, which Tokyo insists was settled in a 1965 accord normalising relations.

The demonstration was echoed in Taiwan, which Japan occupied from 1895 until the war's end, where about 200 Taiwanese chanted slogans and tore up Japanese military flags.

Japan marked the 67th anniversary of its surrender with an official ceremony in which Emperor Akihito and Prime Minister Yoshihiko Noda led 6,000 people in prayer.

Their speeches used tried and tested formulae for regret, but avoided an explicit apology.

"During the war, (Japan) inflicted significant damage and pain on many countries, especially on people in Asian countries," Noda told the annual ceremony. "We deeply regret that."

Akihito said: "Recalling history, I profoundly hope that the suffering of war will never be repeated. I sincerely express mourning for those who lost their lives on the battlefields, and wish world peace and our country's further development."

Less diplomatically palatable were the pilgrimages by two of Noda's cabinet to Yasukuni Shrine in central Tokyo, which honours 2.5 million war dead -- including 14 leading war criminals from World War II.

Those enshrined at Yasukuni include General Hideki Tojo, the Japanese prime minister who ordered the attack on Pearl Harbor and was convicted of war crimes and hanged by a US-led tribunal.

Jin Matsubara, one of the ministers, told reporters he was there "in a personal capacity" and had used his visit to "remember ancestors who established the foundations of the prosperity of present-day Japan".

The pilgrimages were the first on the sensitive anniversary by any government minister since the centre-left Democratic Party of Japan came to power in 2009.

All three prime ministers since then have asked their cabinets to stay away, but Noda's crumbling support seemingly left him without sufficient power to prevent the visits.

North Korean state media said the ministers' actions were an "intolerable insult and mockery of the Asian people who suffered a lot due to the atrocities of Japan".