Soldiers comb Timbuktu for rebels French and Malian forces were trying to secure control of the ancient city of Timbuktu in northern Mali on Sunday as efforts to defeat the Islamist militants gathered speed. Incessant French air strikes appear have to caused the al-Qaeda-linked rebels to retreat from their city strongholds further into northern Mali. Government troops, with help from French soldiers and aircraft, have made rapid advances as they pushed north in recent days, encountering little resistance. On Saturday they captured Gao, which has been under control of the Islamists since last April. Another contingent of soldiers reached the outskirts of Timbuktu, the same night. The troops were proceeding with caution on Sunday after reports that some of the fighters had tried to blend in with the local population in Timbuktu. Rebel positions in the third Islamist stronghold, Kidal, were also reportedly bombed by French warplanes this weekend, though the city remains in the hands of the militants. The nearby mountains may offer the three rebel allied groups - al-Qaeda in the Islamic Maghreb, Ansar Dine and Movement for Oneness and Jihad in West Africa - the best chance to seek refuge and try to regroup. In Paris, a spokesman for the chief of staff said troops from Chad and Niger had been moved across the border from Niger to take control of Gao after French special forces and Malian troops recaptured the town's airport and a key bridge over the river Niger on Saturday. The African forces would "progressively liberate (Gao) from terrorist risk," the spokesman said. The French operation was also boosted by agreement by the US late on Saturday to add aerial refuelling assistance to the logistical aid and intelligence gathering it has been supplying. Analysts say the aerial refuelling assistance is vital and allows French commanders to maintain a high tempo of air transport, supply and air attack missions. There is clear satisfaction in Paris at the speed with which French forces, which now number 2,500 in Mali, have been able to halt the jihadi advance in the direction of Bamako, the capital, and start to retake territory held by the rebels. "This is not a slow waltz, it is a high-tempo break dance," said Francois Heisbourg, special adviser at the Foundation for Strategic Studies in Paris. Speed and rhythm and tempo are of the essence. Yet it is still unclear how much damage has been inflicted on the rebels, who have vowed to drag France into a long war. Since the early days of the conflict, the militants appear to chosen to retreat, rather than try and hold ground and face aerial bombardment. The French military said there had been sporadic clashes with the militants, but it has reported no French casualties since a French helicopter pilot was killed by small arms fire on the first day of the operation on January 11, in the central town of Konna. Mali's military, which has been accused of human rights abuses and is preventing the majority of journalists from entering the country's vast north by road, allowed reporters in to Konna for the first time this weekend. A low-slung town of mud-brick houses, it appears largely deserted, though some residents are returning. Burnt out vehicles struck by French jets and helicopters lie mangled by the roadside. Some of the houses are pocked with bullet shells, and a mosque has a gaping hole in its wall where a shell burst through. The Islamists occupied the town for three days, during which heavy fighting occurred. Allasane Maiga, 23, a Konna resident, said that 25 Malian soldiers were killed by the rebels in the initial fight for the town. "They [the Islamists] said "pick up your dogs and bury them,"" said Mr Maiga. Other residents said the Islamists had come in large numbers, but scattered once the airstrikes began. There were civilian casualties, including some who may have died in the French bombardment. Hamadou Diallo, 70, lives near the mosque, where fierce fighting occurred. His compound is littered with shrapnel and the remnants of small missiles, which he said came from French aircraft. During the air raid, his wife Aminata was hit in the arm and stomach and died soon after, said Mr Diallo, dragging a bloodstained foam mattress from a room as proof. His daughter was also injured, he said.