Syrian television reports that a bomb has exploded on the third floor of the state TV and radio building in the capital, Damascus.
Three people were reported wounded and the explosion caused some damage but state TV continued broadcasting.
Rebel forces took 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 aiming to wrest control of the country’s second city, Aleppo, from the rebels.
The explosion in Umawiyeen Square in central Damascus had “ripped the floor” but had left the transmission of the three Syrian channels unaffected.
Pro-government TV channel al-Ikhbariya showed pictures of staff looking after an injured colleague. In June, gunmen attacked its offices, south of Damascus, killing seven people, including journalists and security guards.
Information Minister Omran al-Zoabi told Syrian TV that national media had been targeted in the “desperate and cowardly” attack. An investigation was under way to find out who planted the bomb inside the building, he added.
State TV’s buildings have also been attacked in many provincial cities, most recently in Aleppo.
The army has surrounded Aleppo, Syria’s commercial capital, and tanks have tried to push into two key rebel-held areas, Salah al-Din and Saif al-Dawla, which lie on the main road into the city.
A rebel commander was one of nine people killed in Salah al-Din on Monday, according to British-based group the Syrian Observatory for Human Rights.