Saudi Arabia has freed a Shia cleric whose arrest provoked protests and sparked calls for a "day of rage" on Friday, human rights activists say.
Sheikh Tawfiq al-Amer was arrested last month for reportedly calling for a constitutional monarchy in the kingdom, which is an absolute monarchy.
He was freed on Sunday after hundreds of Shias protested near the eastern city of Qatif; 26 people were arrested.
The authorities have vowed to crack down on any protests, which are banned.
Correspondents say the move is likely an effort to diffuse anger before the planned "day of rage" on Friday.
There have been a series of small protests in recent weeks by the kingdom's Shia minority in the Eastern Province, where much of the country's crude oil is sourced.
The protesters have been demanding the release of nine Shia prisoners who they say have been held without trial for more than 14 years.
Saudi security forces arrested 26 of the protesters - 22 on Thursday and four on Friday - for taking part in the peaceful demonstrations.
Police in Qatif kicked and beat with batons at least three of the protesters, rights group Amnesty International said.
Among those arrested were Shia activists Hussain al-Yusef and Hussein al-Alq, who have written for the Shia website, Rasid News Network, which often details arrests of and discrimination against members of the minority Shia community.
The nine members of the Shia community in prolonged detention were arrested in connection with the 1996 bombing of a US military complex in al-Khobar in which 20 people were killed and hundreds injured.
According to reports obtained by Amnesty, they were interrogated, tortured and denied access to lawyers together with the opportunity to challenge the legality of their detention.
On Saturday, the Saudi interior ministry issued a warning that the police were authorised to take "all measures needed" against those who took part in demonstrations, marches and sit-ins, which have long been banned in the desert kingdom.
The moves come after the return last month of Saudi King Abdullah to the capital after an absence of several months due to illness.
Amid signs of growing unrest in the region, he unveiled $37bn (£22.7bn) in benefits for citizens, including a 15% pay rise for state employees, as well as extra funds for housing, studying abroad and social security.
Shias, who are mainly concentrated in the eastern of the country, make up about 10% of the Saudi population.
The region borders Bahrain, a Shia-majority kingdom ruled by a Sunni government that has been rocked by anti-government protests since mid-February.