French and Malian troops Monday entered the central frontline town of Diabaly as they pushed north in their bid to flush out radical Al Qaeda-linked rebels who have threatened reprisal attacks. Paris said the aim of the 11-day-old military offensive is the "total reconquest" of Mali, whose north was seized 10 months ago by Islamist hardliners who imposed their brutal version of sharia law in key desert towns. The French onslaught, backed by embattled Malian troops, forged ahead despite threats of further retaliation from jihadists after a stunning hostage attack at a gas plant in neighbouring Algeria resulted in scores of deaths. A convoy of about 30 armoured vehicles transporting some 300 Malian and French troops moved into the key frontline town of Diabaly, 400 kilometres (250 miles) north of the capital Bamako, early Monday, meeting no resistance. Diabaly has been the theatre of air strikes and fighting since it was seized by Islamists a week ago. A colonel in the Malian army said earlier that a "fringe of the Diabaly population adheres to the jihadists' theories and we must be very careful in the coming hours". French television footage from Diabaly has shown charred pick-up trucks abandoned by the Islamists amid mud-brick homes. One resident said the rebels had fled the town which was abandoned by many of its residents, and those remaining lacked food and other essentials. On Sunday French troops buttressed their position as they prepared the drive north, moving into the key central towns of Niono and Sevare. Sevare has a strategically important airport about 630 kilometres (390 miles) northeast of Bamako that could help serve as a base for operations further north. France swept to the aid of the crippled and weak Malian army on January 11, a day after the hardline Islamists made a push towards Bamako in the government-held southern triangle of the bow-tie shaped nation. The crisis in Mali began when the nomadic Tuaregs, who have long felt marginalised by government, launched a rebellion a year ago and inflicted such humiliation on the Malian army that it triggered a military coup in Bamako. In the ensuing political vacuum, the central government lost control of the north to the insurgents, and the Tuaregs were instrumental in helping a triad of Islamist rebel groups including Al Qaeda in the Islamic Maghreb (AQIM) seize control of huge swathes of territory. But the Tuaregs' alliance of convenience with the Islamists quickly disintegrated. AQIM and other Islamists began to run territories under their control like a particularly brutal medieval emirate and imposed a harsh form of sharia law. This spiked fears abroad that the occupied area could become a new haven for terrorists. The Islamists, armed with an arsenal scored from Libya after the downfall of Moamer Kadhafi, have proved a well-armed and formidable foe. "The goal is the total reconquest of Mali," French Defence Minister Jean-Yves Le Drian said in televised remarks on Sunday. "We will not leave any pockets" of resistance. In retaliation to the French assault, a jihadist group run by a former leader of the regional Al-Qaeda franchise, Mokhtar Belmokhtar, attacked a gas plant in neighbouring Algeria. A 72-hour stand-off at the complex came to a bloody end on Saturday, but reports are still unclear on the numbers of dead among assailants and hostages. On Sunday, the assailants, calling themselves "Signatories in Blood", vowed "more operations in all the countries which have taken part in the crusade" against northern Mali if it did not halt immediately. Meanwhile the planned deployment of nearly 6,000 African soldiers continued slowly into Bamako, hampered by cash and logistical constraints. Only 150 African troops had arrived by Sunday. Eight west African nations are contributing to the African mission which is expected to take over the baton from France, and Chad has also pledged 2,000 soldiers. The head of the Commission of regional west African bloc ECOWAS, Desire Kadre Ouedraogo, estimated the cost of an African offensive against the armed Islamist groups at about $500 million (375 million euros). The European Union has pledged 50 million euros to the International Support Mission for Mali (MISMA).