Syrian Defense Minister Dawoud Rajiha, Interior Minister Ibrahim al-Shaar, General Hassan Turkmani, and Bashar al-Assad's brother-in-law Assef Shawkat, who was also the deputy defense minister, were killed on Wednesday after a suicide bomber struck the National Security building in Damascus where ministers and security leaders were holding a meeting.
It is not clear whether the blast was caused by an explosive device planted in the meeting room or by a suicide bomber identified as Rajiha's bodyguard.
Following the death of Rajiha, the Syrian government appointed General Fahd al-Furayj as the new defence minister.
According to Syrian State TV, other officials have been seriously wounded including the head of the national secucrity office.
Liwa al-Islam, a Syrian rebel Islamist group, has claimed responsibility for the attack.
Shortly after the first attack, five explosions were heard near the 4th division HQ in Damascus. The 4th division is commanded by Maher al-Assad, Bashar al-Assad's brother. It is also one of the most trusted and feared brigades in the military.
According to activists the Shami hospital in Damascus, where victims of the bombing have been taken, is surrounded by Republican guard troops.