The near-daily attacks have many traumatised Nigerians questioning whether they can vote for Buhari as he seeks a second term. Others question how the elections can be held in the troubled northeast region.
The new violence is by an offshoot of Nigeria's long-time extremists, Boko Haram.
The Islamic State West Africa Province is the IS group's largest presence outside the Middle East and is estimated to have grown to more than 3 000 fighters.
Nigeria has approved a record $147 million for election security but some polling workers in remote areas have rejected their posts in fear of being attacked.
--AP--