Gunmen detonated back-to-back roadside bombs and clashed with police in central Damascus Saturday in attacks that caused no damage but highlighted the ability of rebels to breach the intense security near President Bashar Assad's power bases.

The apparently coordinated blasts point to the increasing use of guerrilla-style operations in the capital to undermine the government's claims of having full control over Damascus. It also suggests that rebel cells have established a Damascus network capable of evading Assad's intelligence agents and slipping through security cordons.

Assad's regime, however, has displayed no hesitation on the battlefield despite blows such as Damascus attacks and defections of high-ranking military and political figures, including the prime minister earlier this week.

In Aleppo, activists said Syrian forces pressed ahead with an offensive to break rebel footholds in the nation's largest city.