Rebels have attacked Mali's strategic northern city of Gao, a day after they took the provincial capital of Kidal, witnesses and an official said. The move deepens the crisis in the landlocked nation at the feet of the Sahara in western Africa after a coup earlier this month.The two towns are major prizes for the Tuareg rebels, who launched an insurgency in January that was fuelled by the flow of arms from the fall of neighbouring Libya, where many of the rebels had been on the payroll ofex-Libyan leader Muammar Gaddafi. Gao is around 1,200km from the capital of Bamako, where junior officers overthrew the elected government and claimed power 10 days ago.If Gao falls, the only other major city in Mali's north in government hands is Timbuktu. On Saturday, Baba Bore, a radio programmer at the local Radio Alfarouk station in the ancient city, said gunshots were heard earlier in the day.The families of military members stationed at the city’s two camps had evacuated, expecting to be attacked. Shops had closed and checkpoints had been erected on all sides of nearby Timbuktu.In Gao, a journalist at Radio Aadar said the attack began early Saturday."There has been heavy fighting all morning and it’s still going on now,” Ibrahima Ly said at midday. "We can hear heavy arms fire and machine guns.”Most of the fighting is just outside town. There is some fighting near the military camp to the east of town. There has been some fighting in the town itself too but that has been quite light. Everyone is scared and locked up athome.”A government source in Niger who is talking to both sides of the conflict also confirmed the attack. He asked for anonymity as he was not authorized to speak to the press.The force is expected to meet more resistance in Gao, where the majority of troops are from the Bambara tribe. In Kidal, the majority of troops were Tuareg.