The exact figure is unknown, although some estimate it to be in the thousands. This is despite the fact that Falun Gong is not officially allowed by the Vietnamese authorities.

The regime clearly does not want Falun Gong to be another potential point of conflict in the already tangled bilateral relationship with China.

But organising meetings is becoming easier, and group meditation can now be seen in public locations.

In Thong Nhat Park in central Hanoi, a dozen men and women are united in a group breathing exercise, their arms tracing arcs through the early morning mist.

They look serene and undisturbed, but it has not always been the case.

Chinese propaganda against Falun Gong has made an impact, and Vietnamese official media still describes it as an illegal, reactionary religious sect.

"When I first started, it was extremely difficult to be a Falun Gong practitioner," recalls Tran Hieu, a 32-year-old architect.

"Nearly all of us got called in and questioned by the police, who wanted to know how we got involved and who brought Falun Gong to us. Some were so frightened they've quit," he says.

He has been practising Falun Gong for almost five years and describes its impact on his life as "nothing short of a miracle".

"I got married five years ago and was told by my doctor that it would be impossible for me to have children.

"But Falun Gong changed that, and I'm now a proud father of a son," he says.

Silent protest

Like many in Vietnam, Mr Hieu found Falun Gong on the internet and was attracted by the health benefits that the spiritual discipline promises.

On phapluan.org, a Falun Gong website in Vietnamese, members exchange similar extraordinary experiences. They can also learn more about the doctrine, as well as download the exercise manual.

Founded by Li Hongzhi and introduced to the public in 1992, Falun Gong claims to have one hundred million practitioners in more than 80 countries.

Based loosely in Buddhist and Taoist teachings, Falun Gong offers meditation exercises and promotes the core values of truth, compassion and forbearance.

It was banned in China in 1999 after more than 10,000 of its members gathered at the Communist Party headquarters in Beijing in a silent protest against repression.

The spiritual movement was deemed by the Chinese leadership to be "the gravest threat to society for half a century".

But Mr Hieu says: "It teaches us to be good people, to live a correct and useful way - it's not a political movement."

Major embarrassment

Just last week, police in Ho Chi Minh City dispersed a gathering in a city centre park, questioned the participants and confiscated all their materials.

Some allege that China is pressuring Vietnam over Falun Gong.

In the past the Chinese government has reportedly asked foreign states to ban Falun gatherings.

Even in Hong Kong, where it is legal, there have been several occasions when Falun Gong tried to hold meetings in public places but was stopped by the local government, says Willy Lam, a lecturer at the Chinese University of Hong Kong.

But he says, unlike in mainland China, Falun Gong has never been able to come into mainstream Hong Kong society and is therefore "not a threat" to central government.

"In fact, the organisation has weakened and its numbers have gone down," Mr Lam says.

In his opinion, even Beijing no longer considers Falun Gong a major threat, and Vietnam does not need to be overtly nervous about the movement.

"I'm sure the Chinese Embassy in Hanoi is keeping watch," he says.

"But as long as Falun Gong members don't cause major embarrassment to the regime by, say, staging mass protests during foreign official visits, there won't be any bad reaction."

One long-time practitioner in Ho Chi Minh City says Falun Gong followers have been seeking to get the practice legalised for years - but to no avail.

"We need to prove to the authorities that we mean no harm to the society. But it seems to need more time," says Nguyen Nam Trung.

But with a number of contentious issues straining Sino-Vietnamese relations, including territorial disputes, it seems that right now Hanoi does not want to take any chances.

By Nga Pham - BBC News - April 7, 2009