The gunfight late on Thursday in a Riyadh neighbourhood came only a day after three other fighters were gunned down by the police in the Saudi capital.
Though not named, one of the fighters killed was supposedly on the most wanted list of the Saudi security forces.
The shootouts over the last two days were the first reported incidents of unrest in the kingdom since 23 June, when the authorities declared an amnesty for al-Qaida supporters who repented and gave themselves up within a month.
The Saudi authorities had publicised a list of its most-wanted Islamic dissidents in December 2003.
The list initially comprised 26 suspects. Officially, 14 of them have either been killed or jailed since then.
Suspected al-Qaida operatives have staged a wave of deadly attacks in the kingdom since May 2003, more recently targeting foreigners.