In a series of raids in at least 17 cities, Chinese police have arrested more than 70 organizers of a popular spiritual sect that held a massive, peaceful protest outside the headquarters of the ruling Communist Party in April, sect leaders and a human rights group said.

Chinese police ransacked houses, broke statues of the sect's Chinese-American founder and rounded up its local leaders in a campaign that began Monday night, according to the Hong Kong-based Information Center of Human Rights and Democratic Movement in China.

Hundreds of followers gathered today in the southern city of Guangzhou to protest the arrests. In Beijing, an unknown number of demonstrators were detained today outside the Communist Party headquarters, relatives said. Protests also were reported in the northeastern cities of Jinzhou and Dalian, but could not be immediately confirmed.

Members of the exercise and meditation group known as Falun Gong said the arrests, which continued today, came in response to the demonstration by about 10,000 group members in April. That silent sit-in ended peacefully and without arrests, but it shocked Chinese security authorities, who began collecting names and infiltrating the group in preparation for this week's concerted action.

The arrests come during one of the most widespread crackdowns on dissent in China in years. More than 200 dissidents, most of them members of the banned China Democracy Party, have been detained since early May. Fourteen have been sentenced to prison terms of up to 10 years, and 32 others remain in custody awaiting legal proceedings for participating in the first attempt to form an opposition party in Communist China's 50-year history.

China's authoritarian leadership has shown little tolerance for organized opposition groups or other independent movements that could threaten its monopoly on political power.

But the emergence of Falun Gong has been an especially nettlesome problem for Beijing because of the group's size, estimated at more than 10 million, and because of the intense devotion of its followers.

Sects like Falun Gong, an exercise and spiritual practice that believes in an "orb of energy" in the belly, have prospered in China in the past two decades as ordinary citizens seek to fill the moral vacuum in Chinese society following the demise of Communist values.

Falun Gong's founder, Li Hongzhi, left China for the United States in 1998. Followers have often held demonstrations to defend their practices and leader. The Beijing protest in April was sparked when officials in a neighboring city refused to retract an article critical of the sect.

"It's not like if some key contact people are arrested then the others will keep quiet," said Feng Yuan, a Falun Gong organizer in New York, who said local practitioners would decide on their own how to protest the detentions. "They cannot arrest all of the followers because there are so many of them."