The enemies of Syrian President Bashar al-Assad struck at the heart of his regime on Wednesday when a bomb exploded in the national security headquarters in the heart of the capital, killing at least three top security officials, including the defence minister and Assef Shawkat, the leader’s brother-in-law.

Regime forces hit back in a dangerous escalation of what rebels have called the battle for the liberation of Damascus.

According to the UK-based Syrian Observatory for Human Rights, which is in contact with a network of activists across Syria, fierce clashes erupted in several neighbourhoods, including Hajar Aswad and Kafar Souseh on the outskirts of the capital, as well as in Midan, one of the first Damascus areas to rise up against the regime.