The Tibetans' exiled political leadership said Tuesday the region had been turned into a giant prison by China and that an imminent change at the top in Beijing was little cause for optimism.

About 400 Tibetans from around the world came together in the northern Indian hilltown of Dharamshala at the start of the biggest gathering of exiles in four years called to highlight the plight of Tibetans under Chinese rule.

The four-day general meeting is the first since the Dalai Lama, the revered spiritual leader of Tibetan Buddhism, decided to retire from political duties, passing responsibilities to new prime minister Lobsang Sangay.

The speaker of Tibet's parliament-in-exile, which is based in Dharamshala, opened proceedings by denouncing Chinese repression, which he held as the cause of the deaths of 51 Tibetans in a recent spate of self-immolations.

"A state of undeclared martial law continues to remain in force in Tibet," Penpa Tsering told the conclave.

"(China) has converted Tibet into a territory resembling a prison camp."

He added: "The question (is) how and in what ways we, the Tibetan people living in exile, should respond to the tragic situation in Tibet today."

The change of leadership in China later this year is one of the key issues for the delegates, with some observers suggesting president-in-waiting Xi Jinping may be more flexible on Tibet.

"Some people say he might lean more towards reform, while others believe he will maintain the hardline policies," Sangay, who was elected as prime minister last year, told reporters.

"We are not that optimistic because the Chinese government has continued to maintain hardline policies on Tibet... but, as human beings, you should remain hopeful, and the new personnel will hopefully have a new perspective on Tibet."

Sangay, a Harvard-educated international law scholar, arrived at the assembly hall escorted by monks robed in saffron and orange who blew horns as a portrait of the Dalai Lama was carried into the venue.

"We must formulate ways to ensure that the cries and suffering in Tibet do not go in vain," he said before the delegates broke up for group discussions.

The Dalai Lama, who is still seen as the ultimate power in the exile movement, is not attending in line with his theoretical "retirement" from politics, but he will hold a prayer session when the meeting ends on Friday.

Many Tibetans have been deeply shocked by the self-immolations, which contradict Buddhist teachings that all life is sacred, and are frustrated that efforts to negotiate with China have resulted in failure.

Talks with Beijing have been stalled for years, and the government-in-exile faces a tough challenge to convince some Tibetans that it remains relevant, despite having no influence over the situation inside Tibet.

Five decades after the Dalai Lama -- now aged 77 -- fled Tibet for India following a failed uprising in 1959, the exile leaders appear to have few options as they seek a way forward.

"The urgency is very high due to the situation getting worse and worse," Dorjee Tseten, a Students for a Free Tibet leader at the meeting, told AFP.

"We want to find good new tactics, but I do not expect any major political change of course."

Norbu Dhargay, a 62-year-old former parliament member from Boston in the United States, said campaigners would hold to the Dalai Lama's principle of non-violence but needed to be more assertive.

"We must use our strong network and contacts around the world to exert pressure (on China) and mobilise support," he said.

Beijing insists that Tibet is an integral part of China and that the Dalai Lama is determined to split the Himalayan region from the rest of the country -- though he says he only seeks greater autonomy.

"China could offer to re-start talks, as there have been some statements from Beijing suggesting this," Robert Barnett, a professor of Tibetan studies at Columbia University, told AFP.

"But the Tibetan leaders are under pressure to withdraw from future talks because there is no confidence in anything coming from the Chinese side.

"This problem has been exacerbated by the self-immolations, which have made the community very emotional and anxious that nothing is being done."