The arrests were made on Friday in the provincial capital Buraidah which has been witnessing anti-regime protests since October 1.
The protests were sparked by Saudi authorities’ refusal to allow the families of political prisoners to visit their loved ones on the occasion of Eid al-Adha.
Although some of the prisoners were released later, reports said that at least 13 children under the age of 14 remain in custody.
Local activists said they were organizing a march to the residence of al-Qassim’s governor, Prince Faisal bin Bandar al-Saud.
Anti-government protests have intensified since November 2011, when security forces opened fire on protesters in Qatif, killing five people and leaving scores more injured.
Activists say there are over 30,000 political prisoners in Saudi Arabia.
On Monday, rights group Amnesty International censured Saudi authorities for not addressing the “dire human rights situation” in the kingdom.
The group also handed in a paper to the United Nations, which included information regarding a “new wave of repression against civil society, which has taken place over the last two years.”
RA/SHI