The 208 suspects had formed six cells with one plotting an attack on an unnamed oil facility in the Eastern Province, according to Interior Ministry spokesman Brigadier General Mansour Sultan al-Turki.
“Security forces foiled an imminent attack on an oil support installation in the Eastern Province after the perpetrators prepared themselves and set a date,” the statement said.
The most serious threat reportedly centred on plans to import eight rockets into the kingdom.
Half of the suspects arrested were described as “infiltrators” who had moved across the border to Saudi from Iraq.
Earlier this year, Saudi Arabia announced it would create a 35,000-strong dedicated security force to protect its oil fields and installations.