Saudi Shi'ites have staged small protests for about two weeks in the kingdom's east, which holds much of the oil wealth of the world's top crude exporter. It is also near Bahrain, scene of protests by majority Shi'ites against their Sunni rulers.
"Twenty-two were arrested on Thursday plus four on Friday, so the total is 26. This was all in Qatif," said rights activist Ibrahim al-Mugaiteeb, who heads the Saudi-based independent Human Rights First Society.
A Shi'ite activist in the Shi'ite town of Qatif in the Eastern Province said he knew of 22 arrests. Interior ministry officials could not be reached for comment.
Shi'ite protests in Saudi Arabia started in the area of the main city town of Qatif and neighbouring Awwamiya and spread to the town of Hofuf on Friday. The demands were mainly for the release of prisoners they say are held without trial.
Saudi Shi'ites often complain they struggle to get senior government jobs and other benefits like other citizens.
The government of Saudi Arabia, an absolute monarchy without an elected parliament that usually does not tolerate public dissent, denies these charges.
The interior ministry said on Saturday demonstrations violated Islamic law and the kingdom's traditions, according to a statement on state news agency SPA.
The activists said wives and other relatives of around nine men detained since an attack at Khobar in 1996 were ejected from the office of the local governor, Prince Mohammed bin Fahd, on Saturday when they tried to petition for their release.
"They met first on Wednesday with an official and he promised they would have a meeting with the governor. But when they went, he declined to meet and security guards intervened," the Shi'ite activist said.
The Shi'ite website Rasid said they were verbally abused, as an official told them they were lucky the detainees had not been executed. The women started chanting "freedom, freedom".
The U.S. ally has escaped protests like those in Egypt and Tunisia which toppling regimes but some dissent has built up as unrest spread in other Arab countries and Saudi neighbours Yemen, Bahrain, Jordan and Oman.
More than 17,000 have backed a call on Facebook to hold two demonstrations this month, the first one on Friday.
A loose alliance of liberals, moderate Islamists and Shi'ites have petitioned King Abdullah to allow elections in the kingdom, which has no elected parliament.
Last month, Abdullah returned to Riyadh after a three-month medical absence and unveiled $37 billion in benefits for citizens in an apparent bid to curb dissent.