Two female suicide bombers have killed at least 22 worshippers in an attack on a mosque in north-eastern Nigeria, rescue officials have said.

Abdul Mohammed, of the State Emergency Management Agency, said 17 other people were injured in the explosions on the outskirts of the city of Maiduguri, which is the birthplace of Boko Haram.

Co-ordinator Abba Aji, of the civilian self-defence Vigilante Group, said one bomber blew herself up inside the mosque and the second outside as survivors of the first blast tried to flee.

He said the mosque is in Umarari on the outskirts of the city which at is now the command centre of the Nigerian military's war against Boko Haram Islamic insurgents.

Several suicide bombers have blown themselves up in recent months at roadblocks into the city manned by the military and vigilantes.