Maiduguri – Twin bomb blasts have killed at least 18 people at a northeast Nigerian mosque crowded with people observing pre-dawn prayers Friday, a self-defence fighter at the scene said.

The fighter was among rescuers who evacuated bodies while troops cordoned off the zone. He spoke on condition of anonymity for fear of reprisals.

It is the latest in a string of suicide bombings blamed on Boko Haram Islamic extremists who have indiscriminately killed Christians and Muslims they accuse of not following their radical version of Shariah law.

The fighter said there appeared to be only one suicide bomber though “we all heard two explosions” around 05:00 in a mosque in the Jiddari Polo area of Maiduguri, the biggest city in the northeast and the birthplace of Boko Haram.

Nigeria’s home-grown Islamic extremist group has pledged allegiance to the Islamic State group and wants to recreate an Islamic caliphate over a swath of West Africa that sprawls across Nigeria’s border into neighbouring Chad, Cameroon and Niger.

Suicide bombers in all four countries have killed hundreds in recent months. The 6-year-old uprising has left an estimated 20 000 people dead and forced 2.3 million from their homes.

A promised offensive by a multinational army of troops from Nigeria and its neighbours has been delayed for months without explanation.

Nigeria’s police chief warned this week that Boko Haram is building bombs in iPads, laptops and cellphones and leaving them for people to pick up.

Inspector General Solomon E. Arase issued the warning while announcing five suspects were arraigned on Thursday in Abuja High Court in connection with twin bombings in Nigeria’s capital that killed 15 people on October 2.