The three activists, all nationals of Saudi Arabia, were identified as Mohamed Hassan Ahmad al- Zayed, Moufeed Hamza Ali al-Alwan and Khalil Ibrahim Hassan al-Muslim, Saudi-owned Al Arabiya TV reported on Thursday.
During the operation in the oil-rich Eastern Province, three regime forces also sustained injuries, according to a Saudi security spokesman.
The raid came shortly after another operation in Qatif, during which at least seven people were injured, Press TV reported.
The Riyadh regime has recently stepped up politically-motivated arrests, prosecution, and conviction of peaceful dissident writers and human rights campaigners. The regime’s forces have also intensified security measures in Qatif.
Qatif, a region in the Arab country’s Eastern Province, has been the scene of peaceful demonstrations since February 2011. Protesters have been demanding reforms, freedom of expression, the release of political prisoners, and an end to economic and religious discrimination against the region.
The Saudi regime is reportedly keeping more than 2,500 anti-regime activists behind bars as part of a widening crackdown led by Crown Prince Mohammed bin Salman against Muslim preachers, members of the press and intellectuals in the country.