Syria's Defence Minister Daoud Rajha has been killed in an explosion at a national security building in Damascus.

Syrian state television reported that President Bashar al-Assad's brother-in-law Assef Shawkat, the country's deputy defence minister, was also killed in the attack.

According to a Syrian security source, the explosion was caused by a suicide bomb, which went off during a meeting of ministers and security officials.

The same source said the bomber was believed to be a bodyguard for President Assad's inner circle.

The country's Interior Minister Mohammad Ibrahim al-Shaar was among those injured in the attack.

He is now said to be in a stable condition in hospital.

Two rebel groups claimed they carried out the attack, calling it a victory against Assad's inner circle, once seen as an impenetrable force.