The Dalai Lama and other Nobel Peace laureates met Friday for a summit on nuclear disarmament in Hiroshima, the Japanese city destroyed by a US atomic bomb.

The gathering was also expected to draw attention to those unable to attend the annual World Summit of Nobel Peace Laureates, including this year's jailed Peace Prize winner Liu Xiaobo.

Former Chinese student leader Wu'er Kaixi, who was involved in the 1989 Tiananmen Square protests, was expected to join the summit on behalf of Liu, according to organisers.

Liu, who was sentenced to 11 years in prison last December on subversion charges after co-authoring a manifesto calling for political reform in China, was announced as winner of the Nobel Peace Prize in October, enraging Beijing.

US President Barack Obama, who was awarded the 2009 Nobel Prize partly for his commitment to nuclear disarmament, missed the meeting due to a scheduling conflict with the Group of 20 meeting in Seoul and an APEC gathering in Japan.

Former Soviet president Mikhail Gorbachev also cancelled his visit for health reasons.

"This World Summit of Nobel Peace Laureates in Hiroshima carries enormous significance. You are the peace leaders who can create the global awareness we need," said Hiroshima mayor Tadatoshi Akiba in his opening speech.

On August 6, 1945, the US B-29 bomber Enola Gay dropped an atomic bomb that instantly killed tens of thousands in Hiroshima.

"Little Boy", the four-tonne uranium bomb detonated over the city, caused a blinding flash and a fireball hot enough to melt sand into glass and vaporise every human within a radius of 1,500 metres (one mile).

The demand for a world without nuclear arms "must be so strong that world leaders, including those in the nuclear weapon states, will finally find the political will to find... a way to rid the world of this plague," Akiba said.

The presence of the Tibetan spiritual leader and a China democracy activist in Japan this weekend will coincide with Chinese President Hu Jintao's trip to the Asia-Pacific Economic Cooperation forum in Yokohama, just south of Tokyo.

Their visits risk stoking a diplomatic row between Tokyo and Beijing stemming from the arrest of a Chinese trawler captain, whose boat collided with Japanese patrol ships near disputed islands in the East China Sea in September.

The captain's arrest, near the uninhabited islands known as Senkaku in Japan and Diaoyu in China, sparked a barrage of protests from Beijing that continued after Japan released him, sending relations to their lowest point in years.

Asia's top two economies are looking to mend ties after their prime ministers, Naoto Kan and Wen Jiabao, failed at recent summits in Brussels and Hanoi to hold formal talks.

In addition to the Dalai Lama, five other Nobel Peace laureates are taking part in the three-day Hiroshima meeting.

Former chief of the UN atomic energy body Mohamed ElBaradei will be joined by the founding coordinator of an anti-landmine NGO, Jody Williams.

Former South African president FW de Klerk, credited with ending apartheid in the nation and Mairead Maguire, who led a campaign against violence in Northern Ireland, will also attend.

They will be joined by Shirin Ebadi, a lawyer promoting human rights in Iran.