AMMAN (Reuters) - A powerful blast caused by a suicide bomber hit a heavily policed district of the Syrian capital on Thursday with at least seven killed, a police source told state television.

The source was quoted by state television as saying a suicide bomber blew himself in the Kafr Sousa neighborhood where some of Syria’s main security installations are located.

The British-based Syrian Observatory for Human Rights which tracks violence across the country said the death toll was expected to rise with several of the wounded in a critical condition.

Footage on state media showed splattered blood and wreckage of several cars with dozens of heavily armed security personnel at the site of the explosion.

Last July a car bomb also hit Kafr Sousa near an Iranian school in an attack that killed several people in the area, close to the main Umayyad Square that connects the city with several highways.

Insurgents fighting to topple President Bashar al Assad say the district houses many recruits from Iranian-backed militias fighting alongside the army.