SYRIA (CNN) -- With explosives and gunfire, rebels attacked a Syrian building akin to the Pentagon on Wednesday, the second such strike on a military facility in two days.

Four guards were killed and 14 people were injured, including civilians and soldiers, state television reported.

The attack came as a Syrian opposition advocacy group announced a stunning new death toll for the fighting, which has stretched for 18 months.

The government said a fight was under way to "cleanse" the rebels from the targeted building in Damascus -- the office of the joint chiefs of staff -- but military officials are fine.

Activists, however, claimed there were dozens of casualties in the attack. Also, Syrian state television reported that attackers used two suicide car bombs in their assault on the military facility. The Free Syrian Army, a prominent armed group battling government forces, claimed responsibility for Wednesday's strike.

The battle, in the very heart of the capital, is significant because it forces the military to defend what should be among the safest parts of the Syrian government's infrastructure. A strike on such a target has the potential to hurt the confidence of the military and government.

Across the nation, at least 203 people have been killed in attacks Wednesday, including 137 in Damascus and its suburbs. Overall, more than 30,000 people have been killed since the start of the Syrian unrest in 2011, the opposition Syrian Observatory for Human Rights said. The figure includes 21,534 civilians, 7,322 Syrian army forces and 1,168 defectors who joined the rebels, according to the group.

In other reports about attack on the military facility, Iran's state-run Press TV said one of its correspondents was shot and killed and its bureau chief was injured. It was unclear whether it has offices in the building or if the journalists were there covering a story.

Maya Naser, 33, was killed by a rebel sniper, Press TV said. The station's Damascus bureau chief, Hossein Morteza, also was attacked and injured, Press TV said.

The journalists were covering the fighting that ensued after the pair of blasts in the capital, the station said.

"We hold Turkey, Saudi Arabia and Qatar, who provide weapons and militants to kill civilians, military personnel and journalists, responsible for killing Maya," said Hamid Reza Emadi, Press TV's newsroom director.

At least 21 other journalists have been killed covering the Syrian civil war since November, making the nation the most dangerous place in the world for journalists, according to the Committee to Protect Journalists.

On Tuesday, dual attacks rattled a Damascus school building used by Syrian intelligence. The new school year has not started yet.

The brazen assaults on military facilities in the capital city show the resilience of a rebel force that has shown no signs of slowing down despite a brutal government crackdown.

The government blamed the attacks on the military sites on "terrorists," a term it consistently uses to describe anti-regime fighters. It vowed to continue its "unyielding fight" to confront terrorism.