Two suicide bombs struck the heavily guarded Syrian Army headquarters in the heart of Damascus on Wednesday, killing four guards and sparking a gun battle between troops and rebels, state media said.
A rebel officer and a rights group said the audacious attack which also left 14 people wounded was an inside job, while an Islamist rebel group said five of its fighters including a suicide bomber died during the assault.
Iran's Press TV, meanwhile, said one of its correspondents, a Syrian, was killed by sniper fire and its Damascus bureau chief wounded as they reported from the scene.
The attack on the army's operations command center came as the worsening bloodshed, which left as many as 217 dead on Tuesday, dominated proceedings at the UN General Assembly in New York.
"Armed terrorist groups with affiliations abroad this morning carried out a new act of terrorism by detonating a car bomb and another device on the edge of the general staff compound," an army statement said.
"All senior commanders and other officers are safe and sound, and none of them was wounded," the statement carried by state media said.
But state television, citing a military official, said four troops guarding the headquarters were killed, and 14 civilians and soldiers wounded.
The broadcaster showed video footage of a white van exploding beside the headquarters, and a second blast inside the compound. It said the bombings came 10 minutes apart.
"The initial investigation shows that these terrorist explosions around and inside the army headquarters were caused by two car bombs driven by suicide attackers," the military official said.
President Bashar al-Assad's regime has systematically blamed unrest and violence on foreign-backed terrorist gangs since the revolt erupted in March 2011.
The rebel Free Syrian Army's Military Council in Damascus said on its Facebook page that "the Free Syrian Army has struck the military headquarters in Damascus's Umayyad Square."
A rebel officer and the Syrian Observatory for Human Rights said it was an inside job, while an Islamist rebel group said its men carried out the attack. The claims were impossible to verify.