The Dalai Lama voiced sadness on Friday at the reported self-immolation of two more Tibetans, the latest in a wave of such protests against Beijing's rule.

But the exiled Tibetan spiritual leader -- blamed by Beijing for fomenting the burning protests -- was cautious of further comment since the issue was "very political" -- and also said he signs of Chinese political leaders.

"It is very very sad," he said, when asked about the latest two self-immolations in a restive southwestern region of China, reported by human rights in groups.

"Indeed, very sad. But at the same time it is currently (a) very very political issue. I prefer (to) remain silent," he added, during a visit to California.

A total of 34 Tibetans, many of them Buddhist monks and nuns, are now reported to have attempted to kill themselves in the same way since the start of 2011 over what they see as Chinese repression of their culture.

The latest self-immolations by a pair of young Tibetan men occurred Thursday in the prefecture of Aba, in a rugged area of Sichuan province, overseas Tibetan rights groups said.

Beijing last month blamed the Dalai Lama for a violent incident in India that saw one Tibetan exile set himself on fire in protest against a trip by Chinese President Hu Jintao to New Delhi.

"Recently, the Dalai group has been sparing no efforts to incite Tibet independence activities and deliberately create various disturbances," foreign ministry spokesman Hong Lei told reporters on March 27.

"These conducts and deeds clearly show that the Dalai group is single-handedly masterminding relevant self-immolation actions."

The Dalai Lama, who began a US trip in Hawaii before traveling to California this week and then on to Chicago and Canada, meanwhile repeated Friday his view that there were positive signs of political reform.

He cited comments by outgoing Chinese Prime Minister Wen Jiabao, that China has no way forward but through economic and political structural reform, as well as the sidelining of a key hardliner.

"These things show (that) the more open-minded leaders... are gaining the upper hand. So that's a hopeful sign," he told reporters in Long Beach, California.

China has imposed tight security to contain simmering discontent in Tibetan regions since 2008, when deadly rioting against Chinese rule broke out in Tibet's capital Lhasa and spread to neighboring Tibetan-inhabited regions.

Many Tibetans in China complain of religious repression and a gradual erosion of their culture blamed on a growing influx of majority Han Chinese to their homeland.

China denies any repression and says it has improved the lives of Tibetans with investment in infrastructure, schools and housing and by spurring economic growth.

Beijing has repeatedly accused the Dalai Lama, Tibet's exiled spiritual leader, of inciting the self-immolations in a bid to split the vast Himalayan region from the rest of the nation, a charge he denies.

The 76-year-old meanwhile laughed off a question about him visiting North Korea, currently in the spotlight over its recent rocket launch. China is Pyongyang's sole major ally and provides a crucial prop for its ailing economy.

"If some serious invitation come from North Korea then no reason (to) refuse," he said, laughing, before adding: "But impossible."