A car bomb and two other explosions have gone off at the main gate of the Syrian Interior Ministry in Damascus, state television has said.
Earlier on Wednesday, the broadcaster reported a car bomb near the Palace of Justice had killed at least one person.
Al Jazeera's Mohammed Vall, reporting from Beirut, said: "The so-called second battle for Damascus has been raging for a number of days now and we know that the rebels have been able to try and cut off the road between Damascus and the airport."
"Now, explosions are being heard in places where they never took place before."
Vall said that rebels were blaming the "fake explosions" on the government who were attempting to draw attention away from a meeting of the 'Friends of Syria' in Marrakesh.
At the meeting on Wednesday in Morocco, more than 100 countries recognised a new Syrian opposition coalition, further isolating the regime and opening the way for greater humanitarian and even military assistance to the forces battling President Bashar al-Assad.
Vall said reports were still coming in that more explosions had been reported in Damascus.
"The problem here is that the rebels have not announced any claim" to the explosions, he said.
Lebanon's al-Manar television, which supports Hezbollah, said four people were killed and more than 20 wounded in the explosions.
The Interior Ministry is in Kafar Souseh, an area of the Syrian capital that borders the central Ummayad Square and is contested between rebels and forces loyal to Assad.
A resident said she heard sirens and shooting after a "huge explosion". The pro-government TV station Al-Ikhbariya aired footage of concrete rubble, blood on the floor and a two-metre-wide hole in the road.
Rebels have made gains on the outskirts of Damascus recently, but have relied on hit and run attacks and bombs in the centre of the city, often on state security buildings or areas loyal to Assad.
A July 18 bomb attack that killed four of Assad's closest aides, including his feared brother-in-law Assef Shawkat, was followed shortly afterwards by a rebel advance into the capital but they were later pushed back.
At least 40,000 people have been killed in Syria's uprising, according to the Syrian Observatory for Human Rights.
The uprising, which started in March 2011 when street protests were met with gunfire by Assad's security forces, has spiralled into the most enduring and destructive of the Arab uprisings.