By Jason McLure, BLOOMBERG

BHP Billiton was granted a potash-prospecting licence for a 17,000 square-kilometre area in Ethiopia’s Afar region, its Mines Ministry said.

Three British and two French nationals were kidnapped in the Afar region in March by rebels.

Potash is used in fertilizers and to make cement.

Ethiopia, Africa’s biggest coffee producer, is keen to attract investment into its mining industry to diversify its economy.

It has deposits of gold, platinum, gemstones and other minerals, according to the the US Geological Survey.

Potash prices may almost double to $US900 a tonne over the next two to three years amid higher food demand and limited supplies of the soil nutrient, according to Paul Matysek, chief executive of exploration company Potash One.