Militants believed to be linked to Boko Haram sect opened fire on people worshipping inside the mosque in Konduga near Nigeria's restive city of Maiduguri on Sunday, security officials said yesterday.
At least 44 worshippers have been shot dead, they said.
Also, a member of a vigilante group said that some of its members were gunned down by the rampaging terrorists when they tried to respond to a distress call.
It was not immediately clear why the mosque in Konduga was targeted, but Boko Haram has in the past attacked mosques whose clerics have spoken out against religious extremism. The group also has attacked Christians outside churches and teachers and schoolchildren, as well as government and military targets.
Boko Haram aims to establish and Islamic caliphate in the oil-rich country and more than 2000 persons have died since it commenced killings and bombings mostly in the northern part of the country.
Nigeria's 150 million people are evenly distributed among Christians and Muslims.