Police say at least 24 worshippers have been killed in an attack on a mosque in northern Nigeria.

Adamawa State police spokesman Othman Abubakar says an explosion occurred during prayers Tuesday afternoon and many people died as they fled and were caught by a second blast.

Abubakar says the scene in Mubi has been cordoned off by anti-bomb squads and security personnel.

Local residents say they saw a young man wearing a suicide vest entering the mosque with the worshippers. One resident says the mosque's roof was blown off.

Many are blaming the Nigeria-based Boko Haram extremist group for the attack.