SANAA/ADEN (Reuters) - Four people, including three children, were killed overnight when troops loyal to Yemeni President Ali Abdullah Saleh shelled a petrol station in a region north of the capital, tribal sources said on Sunday. Thirteen others were wounded in the attack in the Arhab area, some 40 km (25 miles) from Sanaa, where tribesmen have backed protesters demanding an end to Saleh's 33-year rule. In the city of Taiz, a doctor said one civilian was shot dead and two were wounded by government forces who fired at a car. The incident occurred in a district where there have been clashes between government forces and pro-opposition tribesmen.