Only a handful of participants answered the initial calls for protests, which authorities met with a show of force last weekend. Because of China's pervasive Internet censorship, few people were likely to know about the campaign for ongoing rallies.

Letters posted online by the unidentified organizers said sustained action will show the Chinese government that its people expect accountability and transparency absent from the current one-party system.

"We invite every participant to stroll, watch or even just pretend to pass by. As long as you are present, the authoritarian government will be shaking with fear," said the letter, posted Tuesday on U.S.-based Chinese-language news website Boxun, which is blocked on the Chinese internet.

China's extensive Internet filtering and monitoring will keep most Chinese from knowing about the protest campaign. Twitter and Facebook, instrumental in Egypt's protests, are blocked in China.

Tech-savvy Chinese can circumvent controls using proxy servers or other alternatives, but few of the country's Internet users seek out politically subversive content.

The initial attempt to stage rallies in 13 cities this past Sunday was joined by just a handful of known active participants. China's authoritarian government, ever alert for domestic discontent, stepped up police presence in the streets, disconnected some text messaging services and censored Internet postings about the call to protest.

The source of the online campaign, which first circulated on Boxun, was not known and activists have said they weren't sure what to make of it. The postings call for a "Jasmine Revolution" — the name given to the Tunisian protest movement — and urged people to shout, "We want food, we want work, we want housing, we want fairness" — a slogan that highlights common complaints among Chinese.

Ahead of the called protests this past weekend, human rights groups estimated several dozen to more than 100 activists were detained by police, confined to their homes or were missing.

Several apparently remained in custody Wednesday, including prominent lawyers Jiang Tianyong, Teng Biao and Tang Jitian, and writer Gu Chuan. All of their mobile phones had been switched off, which is common when activists are taken away by authorities.

"We urge the authorities to release the illegally kidnapped activists as soon as possible, otherwise this weekend we will organize another Jasmine Revolution protest on a larger scale to protest the illegal persecution of these people," a letter posted on the Boxun blog said.

Jiang's wife, Jian Bianling, said her husband was taken away Saturday and agents who came to their Beijing home later in the day identified themselves as city police officers and confiscated Jiang's computer.

"I don't know what's going on or where he's being locked up. I'm going to hire a lawyer to help me find him," she told The Associated Press.

Beijing police did not immediate respond to a fax asking whether they had any of the activists in custody.