The 66 people arrested comprise 61 Saudis and a Qatari, Yemeni, Sudanese, Ethiopian and Syrian.
There are 5,305 people with links to terrorist groups in General Investigation prisons, comprising 4,448 Saudis and 857 from other nationalities, including three Qataris, 24 Sudanese, 216 Syrians, 298 Yemenis and four Ethiopians.
Some are serving their sentence, some are in the process of appealing, and others are pending investigation.
Security forces are raiding terrorist hideouts to thwart attacks in the Kingdom.
The latest terrorist attack was on a checkpoint at Al-Salam Palace in Jeddah, in which two royal guards were killed and three wounded. The perpetrator was killed.