The headquarters is protected by concrete blast walls, but the security forces on guard at its entrance on an often-crowded intersection are easy targets for attack.

There was no immediate claim of responsibility for the Saturday blast, but suicide bombings are a hallmark of terrorist groups, including those loyal to the so-called Islamic State of Iraq and the Levant (ISIL) terrorist group.

ISIL, which controls parts of Syria, sent its militants into neighboring Iraq in June and quickly seized large swaths of territory straddling the border between the two countries.

The US has been providing arms and training to militant groups in Syria to fight the government of President Bashar al-Assad.

According to media reports, the militants were trained by the CIA in Jordan in 2012.

RA/SHI