The refugees were queuing to get supplies in the town of Diffa, Nigerian regional officials told Reuters.

The area is home to almost 250,000 displaced people, according to the United Nations. Many of them have fled attacks by Boko Haram Islamist militants and other armed groups in northeast Nigeria.

Boko Haram has been fighting for a decade to carve out an Islamist caliphate and has staged regular raids into neighbouring Chad, Niger and Cameroon, killing thousands. (Reporting by Lanre Ola in Maiduguri and Boureima Balima in Niamey, writing by Anna Pujol-Mazzini, editing by Andrew Heavens)