MAIDUGURI (AFP) — An explosion ripped through a mosque in the northeastern Nigerian city of Maiduguri and killed at least seven worshippers Wednesday, witnesses and security sources told Agence France-Presse.

No armed groups immediately claimed responsibility for what anti-jihadist militia leader Babakura Kolo said was a suspected bombing.

Maiduguri is the capital of Borno state, home to a years-long insurgency by jihadist groups Boko Haram and an offshoot, Islamic State West Africa Province, though the city itself has not seen a major attack in years.

The bomb went off inside a crowded mosque in the city’s Gamboru market, as Muslim faithful gathered for evening prayers around 6 p.m., according to witnesses.

One of the leaders of the mosque, Malam Abuna Yusuf, put the toll at eight dead, though officials have not yet released a casualty count.

“We can confirm there has been an explosion,” police spokesperson Nahum Daso told Agence France-Presse (AFP), adding that an explosive ordnance disposal team was already on-site.

Kolo said that seven were killed.

He said it was suspected that the bomb was placed inside the mosque and exploded midway through prayers, while some witnesses described a suicide bombing.

It was not immediately clear how many people were injured, though witness Isa Musa Yusha’u told Agence France-Presse: “I saw many victims being taken away for medical treatment.”

Videos taken in the aftermath and seen by AFP showed a person covered in blood writhing on the ground, and what appeared to be bodies covered by a sheet.

A security alert sent by an international non-profit to its staff in Maiduguri, seen by AFP, advised its workers to stay away from the Gamboru market area.