The Observatory said the regime used warplanes to hit districts including Daraya, where fighting has raged for days.
The operation around Damascus comes days after rebels made significant advances in the area. Last week, they captured a major helicopter base just outside the capital.
In the southern city of Daraa, where the uprising began, rebels detonated a car bomb near the house of a senior member of the country's ruling Baath Party, killing him and his three bodyguards, activists said. Rebels frequently target regime figures and military commanders.
Associated Press writers Barbara Surk in Beirut, Matthew Lee in Washington, Peter Svensson in New York, Peter James Spielmann at the United Nations, Robert H. Reid in Berlin and Aya Batrawi in Cairo contributed to this report.
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