Protesters demonstrate in the Gulf coast town of Awwamiya, Saudi Arabia, 3 March 2011. (Reuters)
Several hundred people protested on Friday in the Shiite-majority east of Saudi Arabia, calling for the release of an arrested cleric and other detainees, witnesses said.
An appeal was made on Facebook for a "Day of Rage" on Friday in the kingdom's east to demand the release of Sheikh Tawfiq al-Aamer, a Shiite cleric arrested on Sunday.
Hundreds of people protested after Friday prayers in the town of Al-Houfouf for the release of Aamer and others, witnesses said.
A similar protest was held in Al-Qatif but was dispersed by police, witnesses said.
On Thursday night, 22 people were arrested as police dispersed a protest in Al-Qatif that was demanding the release of prisoners, said Ibrahim al-Mugaiteeb, the president of Human Rights First in Saudi Arabia.
"The protesters demanded the liberation of nine 'forgotten' prisoners in Al-Qatif, and also of Sheikh al-Aamer, whose picture they carried, and called for national unity between Sunnis and Shiites," Mugaiteeb told AFP by telephone.
Aamer was arrested "after calling for the establishment of a constitutional monarchy" in the kingdom, which is currently ruled by an absolute monarch, according to the website www.rasid.com, which specialises in information on Saudi Shiites.
Shiites, who are mainly concentrated in the oil-rich eastern province, make up about 10 percent of the Saudi population. They complain of marginalisation in the country, which is dominated by the puritanical Wahhabi Sunni doctrine.
The eastern province borders Bahrain, a Shiite-majority kingdom ruled by a Sunni dynasty that has been rocked by anti-government protests since February 14.
Meanwhile, at least three people were arrested after repeating slogans against the Saudi monarchy in Riyadh, witnesses said.
A dozen men gathered at the exit of the Al-Rajhi mosque, one of the most important in Riyadh, repeating slogans denouncing "oppression" and the monarchy, according to witnesses.
They were attacked by worshippers before the police intervened and arrested at least three people, including one of the leaders of the small demonstration, the witnesses added.
Activists have called on Facebook for a "Day of Rage" on March 11 and for a "Saudi revolution" on March 20.