BEIJING - Hundreds of Tibetans in Lhasa have been detained by Chinese security officers after two self-immolation protests against Chinese rule over Tibet, according to U.S.-funded broadcaster, stoking concerns of spreading unrest among Tibetans in China.

Locals detained are being held in detention centers in and around Lhasa while many of those from outside the Tibet Autonomous Region have been expelled, Radio Free Asia said.

On Sunday, two Tibetan men set themselves on fire in Lhasa, state news agency Xinhua said, the first time in four years of a major Tibetan protest against Chinese rule. One of the men died.

China has branded the self-immolators "terrorists" and criminals and has blamed exiled Tibetans and the exiled Tibetan spiritual leader, the Dalai Lama, for inciting them.

Protesters set themselves on fire near temple popular with tourists in Tibet capital

At least 35 Tibetans have set themselves on fire since March 2011 in protest against China's six-decade rule over Tibet, according to Tibetan rights groups. At least 27 have died.

Hao Peng, head of the Communist Party's Commission for Political and Legal Affairs in the Tibet Autonomous Region, has urged authorities to tighten their grip on the Internet and mobile text messaging, reflecting government fears about unrest during a month-long Buddhist festival which started last week.

The move is the latest in a series of measures the government says are intended to maintain stability.

Video: Are we seeing a Tibetan spring?

Beijing considers the Dalai Lama, who fled into exile in India in 1959 after an abortive uprising against Chinese rule, a separatist. The Dalai Lama says he merely seeks greater autonomy for his Himalayan homeland. 

Reuters contributed to this report.

More world news from msnbc.com and NBC News:

• Will crisis-hit Ireland rebel against harsh remedy for ailing Europe?
• 'Very clear' signs of Iran sanitizing military site, Western diplomat says
• Porn actor wanted for murder over body parts in Canada mail
• Tribesmen release two 2 US tourists kidnapped in Egypt
• Report: Hundreds detained in Tibet after self-immolations
• Israel's Barak tells NBC: 'A nuclear Iran is unacceptable'
• Was Flame virus written by cyberwarriors or gamers?
• Report: Iran using passenger jets to smuggle weapons to Syria, Lebanon
• Nelson Mandela makes rare appearance in home village
• Greek tragedy: Economic crisis sparks brain drain

Follow us on Twitter: @msnbc_world