Chinese security services have detained more than 4,000 people in Beijing alone during a massive, nationwide crackdown against a popular spiritual sect that the government banned last week, Chinese sources said today.

During the past few days, police have removed members of the Falun Gong sect from their homes and group meetings and from buses headed for Beijing. The operation, involving thousands of officers of the People's Armed Police and other security services, is the largest of its kind since People's Liberation Army soldiers flooded Beijing in 1989 to repress student-led protests.

Unlike the 1989 crackdown, however, Falun Gong members detained in Beijing appear to have been well-treated for the most part. Although some have been charged with crimes, most have been released after being held at one of four stadiums in the capital that are being used as temporary detention centers, according to sources with direct knowledge of the operation. In several places outside of Beijing, sources reported that police beat Falun Gong practitioners.

The campaign against the sect has drawn strong criticism from Western human rights groups, which accuse China of violating its laws allowing freedom of religion. China says that the sect is led by an "evil" man, Li Hongzhi, a 47-year-old former trumpet player, bureaucrat and soldier who has claimed he can remove tumors from people's bodies and preaches about the end of the world.

The government, which outlawed the group on Thursday, has justified the crackdown by saying the sect has ulterior political motives. In reality, the main threat from the group appears to have been its extremely well-organized and disciplined membership, built around 1,900 teaching stations and 28,000 practice sites. The Communist Party does not tolerate the existence of organizations outside of its control.

The Communist Party was also alarmed at the large number of its members who joined the group, and has used the campaign against Falun Gong to promote Marxism, atheism and unity within a party struggling to find its ideological bearings in an era when the country is moving toward more of a capitalist economy.

Falun Gong combines Buddhist teachings and predictions about the end of the world with meditation and martial arts as a prescription for physical and spiritual health. Most of its practitioners are retired or unemployed, though its membership also includes a number of highly educated younger followers.

Sources also said that the campaign against the sect began sometime after April 25, when 10,000 of "Master Li's" followers surrounded the central headquarters of the Communist Party in Beijing, calling on the government to grant the organization official recognition. Sources said neighborhood committees -- the lowest level party organization in China's cities -- were instructed to monitor Falun Gong activities in each neighborhood throughout China's cities.

In one neighborhood in Beijing, a special committee was set up linking the neighborhood committee to the local police station, one source said. A list was drawn up of practitioners. Committee members went to the house of each Falun Gong practitioner and warned him or her to cease practicing the breathing exercises in public, the source said.

"In one case they had a retired official, an old Communist Party member," said the source, whose relative participated in committee meetings. "They said, choose the party or Falun. He chose Falun. When they ordered the crackdown, they took him away."

The government has been especially concerned about the involvement of senior police, military and other government officials, including retirees, in the sect's activities.

In a special dispatch on the People's Liberation Army, the New China News Agency stressed that retired officers -- many of whom were followers of Falun Gong -- were a focus of the campaign. Today, 30 veterans who joined the army in the 1930s and 1940s gathered in southern China to condemn the sect.

"We, who experienced the revolutionary wars, see this more clearly than anyone else: Only Marxism can save China, and only the Chinese Communist Party can lead us," the state news agency quoted them as saying.

But despite the detentions, Falun Gong adherents vowed not to give up their faith. Members of the group made several attempts to gather in public today, but were quickly surrounded by police. On the outskirts of Beijing, police searched buses for members who might be coming to Beijing to join protests.

One 27-year-old follower, who was detained with her mother on Wednesday for gathering outside the red-walled compound that houses China's leaders, said she has begun practicing Falun Gong in the tight confines but relative privacy of the family apartment.

"Now we cultivate ourselves at home. We don't go out," she said. "This stuff is in our hearts. We don't need to express it in public."

Police treated them well, and released them one day after they were detained, she said. She has no plans to openly resist the ban on Falun Gong because her faith calls for avoiding confrontation, she said.