Vendors sell goods at the main market in Diffa, Niger, March 23, 2015. Diffa is where Nigerien and Chadian troops fighting insurgent group Boko Haram are based at. (Photo by Joe Penney/Reuters)

A truck transporting people drives past the main market in Diffa, March 23, 2015. (Photo by Joe Penney/Reuters)

Soldiers stop to buy goods at the main market of Diffa, Niger, March 23, 2015. (Photo by Joe Penney/Reuters)

People walk in the main market of Diffa, Niger, March 23, 2015. (Photo by Joe Penney/Reuters)

Vendors sell goods at the main market in Diffa, March 23, 2015. (Photo by Joe Penney/Reuters)

Vendors sell goods at the main market in Diffa, Niger, March 23, 2015. (Photo by Joe Penney/Reuters)

A city official (R) makes a phone call at the main market in Diffa, March 23, 2015. (Photo by Joe Penney/Reuters)

A soldier stands guard in front of a military pickup truck at the main market of Diffa, March 23, 2015. (Photo by Joe Penney/Reuters)

An aerial view shows houses outside the town of Diffa, March 21, 2015. (Photo by Joe Penney/Reuters)