DAMATURU, Nigeria -- A blast detonated by a female suicide bomber tore through a crowded market in the northeastern Nigerian city of Damaturu Sunday, killing at least 15 people, a police representative said. Nobody has claimed responsibility for the explosion, which witnesses said occurred at around 9:30 a.m. local time (4:30 a.m. EDT), but it is the latest in a series of attacks in the past few weeks that bear the hallmarks of the militant Islamist group Boko Haram.

“Fifteen people have been confirmed dead so far, and more dead bodies are being brought to the hospital,” police representative Toyin Gbadegasin said. Witnesses said around 50 people had been injured.

The explosion in the center of Yobe state’s capital came six days after a suicide bomber killed three policemen at a checkpoint on the outskirts of the city.

Also this month, at least nine people were killed in the city by a female suicide bomber as worshippers gathered to mark the Muslim holiday Eid al-Fitr.

Boko Haram controlled land around the size of Belgium at the end of last year, but the group was pushed out of most of that territory by Nigerian troops in the last few months, with military help from neighboring Cameroon, Chad and Niger.

But the militants have since carried out attacks in northern Nigeria and neighboring countries as part of a resurgence.

(Reporting by Joe Hemba; additional reporting by Ardo Abdullah in Bauchi; writing by Alexis Akwagyiram; editing by Larry King)