In pictures: Desert Locusts

Swarms of locusts have been darkening skies across north-west Africa in what the UN warns could be the worst plague in 15 years.

Large swarms containing billions of the voracious insects, have invaded Mauritania, Senegal, Mali and Niger and are now threatening to move southwards towards West Africa.

Photos courtesy of Gianpiero Diana of the Food and Agriculture Organization (FAO)