A bomb has exploded on the third floor of the Syrian state TV and radio building in the capital, Damascus, Syrian television reports.
Three people were reported wounded and the explosion caused some damage but state TV continued broadcasting.
Hours later, state TV reported that Prime Minister Riad Hijab had been fired. Appointed two months ago, he had been seen as a staunch loyalist.
His replacement, Omar Ghalawanji, will reportedly lead a caretaker government.
The developments come as Syria's army tries to recapture the city of Aleppo.
Rebel forces took over several areas of Damascus in recent weeks, but the army has since regained control of the capital.
'Desperate and cowardly'
A BBC Arabic reporter in the capital said 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 BBC's Jim Muir reports from neighbouring Lebanon.
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.
Activist group the Local Coordination Committees (LCC) posted footage of what it said were warplanes attacking targets in Aleppo.
A spokeswoman for the exiled opposition Syrian National Council (SNC) told French radio station Europe1 that Aleppo was undoubtedly facing "carnage", with a regime deploying its full military might, including its air force, against lightly armed rebels using guerrilla tactics.
Bassma Kodmani said that Qatar, Saudi Arabia and possibly Libya as well were helping to supply "certain kinds of light and conventional weapons" to the rebels, who were also buying arms on the black market.
The SNC also reported that 40 people were killed when troops and militia bombarded the village of Harbnafsa in Hama province in central Syria. Other opposition groups said 11 people had died, including five children.
Such reports are impossible to verify as access for foreign journalists has been severely restricted.