Sa’ad al-Faqih, the head of the Movement for Islamic Reform in Arabia, said on Wednesday that the number of jailed activists ranged from 25,000 to 30,000.
Faqih also accused the government of stepping up the crackdown on dissent since the beginning of the year.
The Saudi activist said the crackdown is a response to online videos that criticize the ruling Al Saud family and censure the increase in corruption and injustice across the country.
Protests against the Al Saud family have intensified since November 2011, when security forces opened fire on protesters in Qatif in Eastern Province, killing five people and leaving scores more injured.
Last October, 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.”