The BBC's Mark Doyle in Mali says a big international troop build-up is continuing ahead of a probable French-led air and ground offensive on Gao and other desert cities.

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Now if only he had a saying about glittering cities in the desert, I might be able to make a call on this remarkable place: Dubai.

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Meanwhile, the Egyptian government has concentrated its development spending in the big cities and on desert-reclamation schemes, while channelling private investment into industry and property in the north.

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The French-led operation in Mali has ousted the Islamist groups, including al-Qaeda's North African branch, from cities and town in the vast desert region they had captured a year ago in the wake of a coup.

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Apple Maps misplaced airports, hospitals and entire cities, the latter leaving some drivers stranded in the Australian desert.

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Since the intervention began, major cities including Gao, Kidal and Timbuktu have been recaptured but fighting is still continuing in desert mountains.

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Although the policy of clamping down on illegal immigration in cities is working, federal officials are surprised at the amount of traffic that has been diverted to the desert.

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Some towns and cities have been recaptured by French soldiers but a number of Islamist fighters are believed to remain in their desert hideouts in the north from where they launch isolated attacks against French and Malian forces.

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