Two female suicide bombers blew themselves up on Wednesday in the Niger frontier town of Diffa, two security sources said following days of cross-border attacks by Nigerian Islamist group Boko Haram.

One of the sources said he believed there were no other victims in the attack but it was not possible to immediately verify the information.

In Gamboru Ngala, 13 Boko Haram fighters were killed by Chadian soldiers in a battle in the Nigerian town of Gamboru on Wednesday, the army said in a statement.

However, one Chadian soldier was killed.

Chadian troops are in Gamboru as part of a regional offensive against Boko Haram, whose militants have started staging cross-border raids in addition to attacks inside Nigeria as part of a campaign to establish a caliphate.