Their mountain hideout was equipped with food and cameras and had a stockpile of arms, the statement said.
State TV footage showed the seized weapons included automatic machine guns, explosive belts and ammunition.
"They were almost ready to start with acts against the kingdom," interior ministry spokesman General Mansur al-Turki told the AFP news agency.
"They were not arrested at once, but taken one by one, until we were certain we had all of them," he said.
The ministry did not elaborate on whether the group were connected to a list of 85 men thought to be planning attacks against Saudi Arabia.
That list, released by Saudi officials in February and followed up by an Interpol alert, included 83 Saudis and two Yemenis.
Some of those on the list were thought to have links to al-Qaeda in Saudi Arabia, Iraq and Afghanistan, and they were thought to be planning attacks on oil and security facilities in Saudi Arabia.
