A Buddhist sect led by a world-renowned Vietnamese monk has been driven out of a monastery in Vietnam's southern highlands in what sect members say is an official crackdown.

Supporters say around 100 police and plainclothes thugs evicted more than 350 Buddhist monks and nuns by force last Sunday from the hillside monastery in the town of Bat Nha. The followers, many of them in their twenties, then found refuge in another, smaller temple in nearby Bao Loc but say they are now being pressured again to leave by local authorities.

In recent years, communist-ruled Vietnam has begun to loosen its grip on sanctioned faith groups, while keeping a close watch on dissidents. In 2006, the US State Department took Vietnam off a blacklist of countries that severely limit religious freedom, a move that human rights groups called premature. Now, followers of the popular sect are asking for the US and other governments to intervene, arguing that Vietnam is persecuting them.

"We see clearly that they don't want our young nuns and monks to stay together and practice as a community," says Trung Hai, a monk in France who is in contact with the 354 followers holed up in the temple near Bao Loc. He says they are fearing for their safety.

Recent crackdown on sensitive subjects

The recent religious tensions follow the detention of several Vietnamese bloggers critical of relations with China and other politically sensitive issues. An independent public-policy research center also closed down. Some analysts have linked the crackdown to intraparty jostling ahead of a 2011 party congress.

It's unclear if the attacks on the Buddhist sect fit this pattern. Followers say tensions have been rising for months after the monastery's abbot, who initially welcomed the sect, turned against them, allegedly at the behest of Vietnamese authorities suspicious of its teachings and their popularity.

Sect founder: exiled best-selling author

The sect was founded by Thich Nhat Hanh, a best-selling author who lives in exile in France and helped popularize Buddhism in the West. In 2005, he was allowed to return to Vietnam after more than three decades in exile, including stays in the US where he joined protests against the Vietnam War. (Read more about Nhat Hanh here.)

During a second visit in 2007 he established a permanent teaching center in the town of Bat Nha, around 87 miles from Ho Chi Minh City. The sect began to expand, attracting young educated Vietnamese drawn to its emphasis on simplicity and social engagement. Most of the monks and nuns driven from the monastery are in their twenties or younger. Two older monks have been detained by police, according to the sect.

Nhat Hanh has criticized Vietnam's curbs on religious freedom, making him a potential target for communist hard-liners fearful of the power of faith-based groups. Another possible reason, says Trung, is his public support last year for Tibetan Buddhists in China, a stance that may irk pro-China leaders.

Internal dispute between Buddhist sects?

Authorities have not commented on the latest twist in the dispute, but have said previously that it was an internal matter between two Buddhist sects.

After the communist victory in 1975, all Buddhists in Vietnam were ordered to join the Buddhist Church of Vietnam (BCV) or face persecution. Similar rules applied to other sanctioned religions. Both the Bat Nha monastery and the temple are under the BCV, and Nhat Hanh has distanced himself from a banned Buddhist group whose members have repeatedly been detained by authorities.