Saudi security forces patrolled a residential suburb of Riyadh on Monday where police defused a grenade, Saudi security sources said.
The bomb was placed in a shop selling mobile phones in the middle-class, predominantly Saudi Sultana district near the Suweidi neighbourhood where police previously clashed with militants.
The militants are believed to be linked to Osama bin Laden's al Qaeda network. At least 50 people have been killed in suicide attacks on Riyadh housing compounds since May 2003.
Dubai-based Al Arabiya television channel, which is partly Saudi-owned, said police foiled a bomb attack on an electricity distribution unit in the area. The Saudi newspaper al-Riyadh, quoting witnesses, said police had found the grenade inside the power supply box of a building.