Amnesty International complained Friday that at least six men remain imprisoned in Saudi Arabia for planning to take part in protests a year ago.
Saudi activists declared March 11th last year as a "Day of Rage" to emulate other protests in the region. By then, the "Arab Spring" uprisings had ousted authoritarian leaders in Tunisia and Egypt.
The London-based group said in a statement that only one of the men arrested is thought to have actually protested, while most have not been charged.
Philip Luther, the Amnesty director in the Middle East, said, "holding people for a year merely for intending to protest is completely unconscionable."
"It is time for the authorities to come clean about who is being held for acts of protest and on what basis," he said in a statement.
Amnesty said at least one of the men was believed to have been tortured in prison. The group urged Saudi authorities to investigate reports of torture and prosecute those held responsible for abuses.
There have been frequent demonstrations over the past year in the oil-rich Qatif region, where most of the residents are Shiites, who overall make up a minority of 10 percent in the kingdom.
They complain of discrimination by Saudi Arabia's Sunni rulers.
At least five protesters have been killed in clashes with Saudi security forces since November. Officials have blamed foreign meddling, an apparent reference to Shiite Iran, its main regional rival.
The conservative kingdom is often criticized by rights groups for curbing freedoms, especially of women and religious minorities.