Security forces opened fire as thousands of anti-government protesters took to Syria's streets in a weekly ritual of defiance and demands for Syrian President Bashar al-Assad's ousting.

Activists said at least 15 people were killed and many more injured in demonstrations following Friday prayers.

People had barely come out of Ibn Affan Mosque in the Damascus suburb of Al Qusweh, chanting for a toppling of the regime when security forces, apparently without warning, opened fire on the crowd killing, six people and wounding 15, Mohammed Suliman, a human rights activist, told Al Jazeera.

Suliman said that ambulances drove the wounded to the headquarters of the military secret service, rather than the hospital.

"We have protested peacefully in Al Qusweh for three months and now we are being accused of having gangsters among us - but we have none.