"Security forces uncovered a group of wanted men who belong to the deviant group (militants) in the Khodeira area of Buraida," the ministry statement, read on Saudi television said, adding one militant and two policemen were also wounded in the exchange of gunfire.
The authorities normally use the phrase "deviant group" to refer to followers of Saudi-born al-Qaida leader Usama bin Ladin, blamed for a string of bomb attacks in Saudi Arabia and the September 11, 2001, attacks in the United States.
Buraida, a town north of Riyadh, is viewed as the heartland of radical Islamists linked to bin Laden bent on bringing down the US-allied monarchy.
In the latest of a series of attacks over the past year, five foreigners were killed in an unprecedented armed assault on a petrochemical site on Saudi's west coast earlier this month.
There have been recurrent clashes between Saudi security forces and suspected Islamists. They have killed and arrested dozens and seized numerous arms caches.
Fifty people were killed in Riyadh last year in bombings blamed on al-Qaida.
Security forces have killed or arrested eight on a list of 26 top suspects since December. It was not clear if the four men were on the list.