Syrian rebels detonated two suicide car bombs at President Bashar al-Assad's heavily guarded army headquarters in Damascus Wednesday, killing four security guards and sparking a gunbattle in which an Iranian journalist also died.

Security video aired by Syrian state TV showed a white van driving on a busy street outside the military compound, then veering to the right and exploding. The video showed a second blast going off inside the complex.

The Britain-based Syrian Observatory for Human Rights said that after the second explosion, rebel fighters and government forces exchanged fire for more than three hours.

Syrian state TV reported that four army guards were killed and 14 people were wounded, including civilians and military personnel. Iran's Press TV said one of its correspondents was killed by sniper fire and the Damascus bureau chief for another state-run news organization was wounded reporting on the bombings.

Information Minister Omran Zoubi blamed the attack on terrorists, a term the government uses for rebels opposed to Mr. Assad.

The explosions are the latest to hit the capital during the country's 18-month conflict, following a bombing Tuesday at a building occupied by pro-government militias. Rebels said they hoped that attack would kill top-level security officials.

Last month, bombings struck the state television headquarters in Damascus and near a hotel used by United Nations observers. A bomb attack in July killed Syria's sitting defense minister and three other top security officials.

World leaders speaking at the annual session of the United Nations General Assembly on Tuesday called for an end to the conflict in Syria.

U.N. Secretary-General Ban Ki-moon told the assembly the world must “stop the violence and flows of arms to both sides, and set in motion a Syrian-led transition as soon as possible.”

France called for U.N. protection of rebel-held areas to help end Syria's bloodshed and rights abuses.