The cell consisted of 31 suspects, including four foreign residents, who were detained during a "preemptive" security operation in Riyadh on September 12, the ministry said.
The group had been "on the verge of acting, after issuing fatwas legitimising the abduction of innocent people ... killing them, and raiding banks", the ministry said.
Another 44 Saudis were detained on October 26 in a series of simultaneous security operations in Riyadh, the oil-rich eastern province, and the northern regions of Al-Qassim and Hail, the ministry said.
Saudi Arabia announced last February that it had thwarted a bid to blow up the world's largest oil processing plant at Abqaiq, also in the eastern province.
Western coalition forces said in October they feared possible attacks on oil installations in Saudi Arabia and other Gulf countries.