Suspected terrorists exchanged fire with Saudi security forces raiding a house in Riyadh on Thursday, killing several Saudi agents, an Interior Ministry official said. One suspect was arrested.

The shootout came amid heightened security as about 2 million Muslims from around the world flocked to the Saudi kingdom for the start of the annual Muslim pilgrimage to Mecca, or hajj (search).

Security forces had received a tip about the house in an eastern section of the Saudi capital and came under fire when they arrived, said the official, speaking on condition of anonymity.

He said one suspected terrorist was captured and an unspecified number of security agents were killed. The official gave no further details.

Saudi authorities have carried out numerous anti-terrorism raids in recent months, particularly since last year's bombings of two housing compounds for foreigners in Riyadh (search). Saudi and U.S. officials blamed both on Al Qaeda, whose leader Usama bin Laden is a Saudi exile.

Authorities have detained hundreds of people in the crackdown on alleged militants and urged wanted persons to surrender. Saudi officials also has more publicly tried to discourage extremism in the kingdom, airing television footage of alleged militants repenting of their crimes.