An explosion tore through a mosque during evening prayers on Wednesday in Maiduguri, the capital of Nigeria’s Borno state, a Reuters witness said. There was no immediate word on casualties or official comment.

Maiduguri has long been the epicenter of a nearly two-decade insurgency led by Boko Haram, founded in the city in 2009, and its splinter faction, Islamic State West Africa Province (ISWAP).

An explosion in a mosque in Maiduguri, northeastern Nigeria, killed at least seven worshippers. The blast, suspected as a bombing, highlights ongoing threats from Boko Haram and ISWAP insurgents.