Syria's rebel Free Syrian Army (FSA) claimed responsibility for a deadly Damascus attack on Wednesday that killed two top regime figures, the defence minister and the president's brother-in-law.
The command of the FSA "announces the good news of the outstanding operation this morning that targeted the National Security headquarters and the killing" of the officials "responsible for barbaric massacres," it said in a statement.
Officials said the bomber struck as ministers and security officials were meeting at the heavily guarded National Security headquarters in Damascus.
Defence minister General Daoud Rajha and Assad's brother-in-law Assef Shawkat were killed and interior minister Mohammed al-Shaar and General Hisham Ikhtiyar, head of National Security, were wounded, state television and security officials said.
The FSA statement made no reference to how the officials were killed.
The rebels said this operation "is the first in a series ... aimed at bringing down Assad and the pillars and symbols of the regime, whether civilian or military."
The statement recalled the ultimatum the FSA had issued "to all those who do not have blood on their hands" to defect before the end of July, or else be deemed "accomplices with Assad in the murders."
The FSA's command also said the killings were "part of the Damascus volcano and earthquakes of Syria operation" launched on July 16.
The FSA announced the launch on Monday night of a full-scale attack operation "in response to massacres and barbaric crimes" of the regime, and said it started to conduct "attacks on all security stations and branches in the city and the countryside."
The offensive was launched hours after fierce fighting started to engulf several districts of the capital, in what has widely been described as a "turning point" in the anti-Assad revolt.