Security forces in the Syrian capital increased checkpoints, troop deployments and helicopter patrols Saturday in a bid to keep an overnight surge of antigovernment protests in the suburbs from spreading to the heart of Damascus, a crucial stronghold for President Bashar Assad.

The beefed-up deployments came as Iran, Syria's closest ally, for the first time publicly pressed Assad's government to accede to the "legitimate" demands of the Syrian public.

Damascus and the commercial city of Aleppo are key centers of support for Assad's government. Large protests in either city would be seen as a sign that Syria's better-off business people, regarded as still largely loyal to Assad, have turned against him. But at least one counter-rally by his supporters Saturday in a southern suburb of Damascus indicated that the president retains an unmeasured but significant amount of backing.