Reports from Syria say security forces have killed six people after storming a mosque in the southern city of Deraa.

Locals say heavy gunfire and tear gas was used shortly after midnight, but the government says that its security forces only moved in to prevent an "armed gang" from attacking.

It's the worst violence in a week of anti-government protests in the city, and represents the strongest challenge yet to President Bashar al-Assad's rule.

Al Jazeera's Omar al Saleh reports.