A loud blast was heard after midnight Monday in the Damascus district of al-Mazzeh, the second to rock the capital within hours, witnesses say.

The blast's exact location wasn't immediately figured, but it came just hours after a suicide bomber detonated his car near the air force intelligence compound in the Damascus' suburb of Harasta, which has reportedly left material damages.

Both blasts were followed by gunshots, in what appeared to be clashes with some armed groups that have intensified their assaults in the capital over the past couple of days at a time the Syrian troops is carrying on with wide-scale offensives nationwide to root out armed insurgency.

The previous blast occurred Sunday evening, when a booby-trapped car ripped through the garage of the police headquarters in the capital Damascus and killed one police officer.