Syrian television is reporting a bomb has exploded on the third floor of the state television and radio building in the capital, Damascus.
Three people were reported wounded and the explosion caused some damage but broadcasting continued.
Rebel forces had taken over several areas of Damascus in recent weeks, but the army has since regained control of the city.
More than 20,000 troops are now trying to take back control of the country's second city, Aleppo, with heavy bombardment of rebel-held districts.
Government forces are using fighter planes, helicopter gunships and heavy weapons to attack districts held by the rebels.