Islamic State on Saturday said it carried out a morning attack on the northeast Nigerian city of Maiduguri as the country holds elections, although the army has denied an attack took place and says sounds of fighting were drills.

In a statement on its news agency Amaq, the militant group’s West Africa Province said the attack targeted Maiduguri airport, a Nigerian army base and a government building.

However, the Nigerian army has denied any attacks took place and said the sounds were of military exercises