Syrian forces killed at least six people on Wednesday in an attack on a mosque in the southern city of Deraa, the site of unprecedented protests challenging President Bashar al-Assad's Baathist rule, residents said. Those killed included Ali Ghassab al-Mahamid, a doctor from a prominent Deraa family who went to the Omari mosque in the city's old quarter to help victims of the attack, which occurred just after midnight, said the residents, declining to be named. Before the attack, electricity was cut off in the area and telephone services were severed. Cries of "Allahu Akbar (God is the greatest)" erupted across neighbourhoods in Deraa when the shooting began. It was not immediately clear whether the protesters had any weapons. The attack brought the number of civilians killed by Syrian forces to 10 during six days of demonstrations calling for political freedoms and an end to corruption in the country of 20 million. The ruling Baath party has banned opposition and enforced emergency laws since 1963. No comment was immediately available from the government of Assad, who is facing the biggest challenge to his rule since succeeding his father, Hafez al-Assad, in 2000. A wave of Arab unrest has toppled leaders in Tunisia and Egypt.