America has launched a secret war against Islamic terrorists across the southern Sahara after it discovered that a group linked to al-Qaeda bought heavy weapons using the proceeds of a ransom deal with the German government.

The realisation that a new Islamic fundamentalist force was building what officials call "garrisons in the sand" on the border of Algeria and Mali has led America to launch a new anti-terror campaign across a swathe of Africa's harshest and most sparsely populated terrain.

The Salafist Group for Preaching and Combat has spent about £4 million, which it received in return for releasing 17 European tourists kidnapped last year, on surface-to-air missiles, heavy machine-guns and mortars.

It also bought satellite positioning equipment to enable it to conceal and later return to weapons caches buried in the sands of the Sahara...

...The US Army plans to spend $125 million (£72 million) over the next five years on its Trans-sahara Counter Terrorism initiative, aimed at preventing groups allied to al-Qaeda from establishing a foothold in the region.

American special forces are being deployed discreetly in the region - which covers eight countries and thousands of miles of desert - to train, advise and equip pro-US government troops.

In a significant breakthrough in March, the US military helped orchestrate the ambush and capture in western Chad of Amari Saifi, the Salafist group's leader.

Brahim Tchouma, for the Movement of Democracy and Justice, the pro-US rebel group that is holding Saifi, told The Telegraph that they were prepared to hand the former Algerian paratrooper to America or its allies.

"They were only lightly armed and travelling in two groups in areas controlled by our movement after a fight with the Chad army. We have them and will hand them over. We want nothing in return."...

...The group is also believed to have a terrorist presence in Europe. Its members have been arrested in Italy, Spain and Germany for suspected terrorist activity.

Governments in the Sahara region were furious when Germany approved payment of a €6 million (£4 million) for the hostages, who included Germans, Austrians and Swedish tourists.

Berlin has never officially acknowledged the deal, but it is widely believed that the government of Mali paid the ransom in return for a promise of additional aid from Berlin.

A Western diplomat said: "This sum was equivalent to 25 per cent of the defence budget of Niger last year. That gives the extremists a huge boost, an advantage which they can exploit to destabilise these governments.

"Once al-Qaeda-linked groups can cause instability, or preferably chaos in a country, they have the ability to operate freely within it."