Defiant Buddhist monks banned from marking a key Tibetan New Year prayer festival marched in protest in China's southwest, rights groups and officials said. It was the latest resistance to Chinese rule ahead of sensitive anniversaries in Tibet.

Tensions are high over harsh security measures set up before the new year, which began Feb. 25. The Monlam prayer festival started on Saturday and ends on March 11th.

The usually merry atmosphere has been largely subdued since the Dalai Lama, Tibet's spiritual leader, said celebrations would be "inappropriate" after deadly anti-government riots in Tibet's capital, Lhasa, last March led to a crackdown on protesters in Lhasa and Tibetan communities throughout the region.

Also approaching is the March 10 anniversary of the 1959 Tibetan uprising that sent the Dalai Lama into exile.

Many Tibetans reportedly have heeded the call to boycott this year's festivities.

The latest protest began Sunday morning — the second day of Monlam — when Chinese officials stopped the monks at the Sey monastery in Sichuan province as they gathered to pray, the International Campaign for Tibet said, citing unidentified sources. The monks left the prayer hall and started walking toward the main town, shouting to be allowed to pray, ICT said.

A few minutes later, armed security officials arrived and the monks returned to their lamasery, the Washington D.C.-based rights group said in an e-mail statement.

ICT's sources said about 600 monks were involved in the latest protest, while another rights group, Students for a Free Tibet, said 50 monks took part.

"They are now surrounded by armed police personnel and are likely to be under lock-down after the protest," ICT said.

An official surnamed Nong at the Communist Party's propaganda office in Aba county said Monday that "no such thing happened." Another official at the party's propaganda office in Aba prefecture, which oversees the area, said he had not heard about the incident.

Several Aba residents and hotel clerks who answered calls said they had not seen anything.

Information on politically sensitive topics like Tibet is difficult to obtain from authorities and ordinary citizens, who often fear official retaliation if they talk. The region is sealed off to journalists and foreigners for the new year period, and the presence of paramilitary police has noticeably increased in Tibetan communities in western China in recent days.

Tibet's self-proclaimed government-in-exile in Dharmsala, India, confirmed that the protest occurred but said no details were available.

"It's sad," said spokesman Thupten Samphel. "These actions show the religious intolerance shown by the Chinese authorities."

Last week, a monk from the nearby Kirti monastery in Aba reportedly was shot after setting himself on fire to protest the prayer ban and restrictions on religion. It was not immediately clear who shot him. Chinese authorities on Monday denied that police had been involved in the shooting, the official Xinhua News Agency reported.

Rights groups said telecommunications — both landline and cell phone signals — have been disrupted in the area since before the Tibetan new year began.

"We have definitely noticed communications comes and goes. The lines are cut when something happens, but it's not forever. It comes and goes based on the sensitivity at the time," said Lhadon Tethong, executive director of the New York-based Students for a Free Tibet.

China banned the Monlam prayer festival during the 1966-1976 Cultural Revolution, when most religious practices were outlawed. The weeklong ceremony, also known as the Great Prayer Festival, was prohibited again in 1990, the year after Beijing launched a crackdown on anti-government protests in Tibet.

Despite the tensions, China insists Tibet has benefited from its rule. On Monday, the Cabinet released a government paper that said Beijing's defeat of the 1959 pro-independence uprising brought much-needed political reform.

"Without the democratic reform, there would have been no emancipation of the laborers constituting 95 percent of the Tibetan population, no frog-leaping social progress and human rights development ... and no happy life for all the ethnic groups in Tibet today."

At an exhibition in Beijing marking the 50th anniversary of the event, photos and documents described how the Chinese leadership and soldiers had helped the Tibetans.

"Before 1959," read one poster, "Tibet was a dark and cruel place."