As hunger strikes go, the 48-hour fast that Fowzan Mohsin al-Harbi and 39 other Saudis plan to stage this week is not likely to have a dramatic outcome.

Rather, says the mechanical engineer, the rare public protest is meant to make a statement about the prolonged detention of 11 men who had called for political reforms in this country.

"It's just a symbol to [draw] attention to our case," says Mr. Harbi, who works at King Abdul Aziz City for Science and Technology in Riyadh. "Yeah, I'm afraid," he adds. "But what can we do? We have to ask for our rights.... We have to move, like every people in the world."

In a sense, the hunger strike is a "virtual" protest. Organizers are publicizing it on Facebook.com and their own website. Word is also being spread by several Saudi bloggers.

This online communication is key since the participants plan to refrain from all food and drink in their own homes Thursday and Friday, the weekend here, so as to avoid violating a ban on unauthorized assemblies.

"If we get in one place, we might get in trouble," says Mohammad Fahd al-Qahtani, a professor of economics who also hosts a local television program.

"It's the first time that activists are doing something like this," Mr. Qahtani says of the online publicity. "Now we are using new tactics."

The protest, said to be the first of its kind in recent memory, tests the boundaries of what is permissible in Saudi Arabia, an absolute monarchy that forbids political parties and rallies.

Under King Abdullah bin Abdul Aziz, Saudis have been allowed to openly discuss reforms in such areas as education, women's rights, labor rules, economics, and domestic abuse. But there is little tolerance for political dissent, and harsh criticism of officials is often severely punished.

Interior Ministry spokesman Gen. Mansour Turki declined to comment, saying that he was unaware of the hunger strike and did not have information on the 11 detainees' current status.

Similarly, a spokesman for the government-appointed Human Rights Commission said he could not comment. "We can't comment on anything we don't know anything about," says Zuhair al-Harithy.

Perhaps the best-known of the 11 detainees is Matrouq al-Faleh, who was arrested in his office at Riyadh's King Saud University, where he teaches political science, in May. His arrest came two days after he published a scathing online report about prison conditions.

The other detainees include a human rights activist detained in December, and nine residents of Jeddah arrested in February 2007. The Interior Ministry has suggested that the men were involved in illicit funding of militant networks. But they have not been publicly charged. Most of the Jeddah detainees were known for their advocacy of political reforms.

Human Rights Commission spokesman Mr. Harithy says the Commission has spoken to the Interior Ministry about the detainees, and "were promised the cases will be solved soon."

Christoph Wilcke, who follows Saudi events for the New York-based Human Rights Watch, said in an e-mail that the protest is a "potent sign" of failure by the Saudi judicial system.

"The Jeddah group of reformers and Matrouq al-Faleh have been arrested for their public and private calls for reform," he says. "But the law and the courts have failed to protect their human right to peacefully express their opinions."

The strikers include friends and relatives of the detainees, as well as Saudis with a general concern about human rights. In an online statement, they said their demands were simple: "Set the detainees free or instantly grant them fair and public trials."