Forty-five people were killed by suspected Boko Haram gunmen pretending to be preachers in a village near the group's spiritual home in northeast Nigeria, two residents told the AFP news agency.
The attack happened at about 20:30 GMT on Wednesday in Barderi, on the outskirts of Maiduguri, and saw the fighters hoodwink locals into congregating before opening fire on the crowd.
Itinerant preaching is commonplace in mainly Muslim northern Nigeria and the fake clerics reportedly told villagers that they had come to show them "the righteous path".
Mallam Bunu, who survived the attack, said: "I counted 45 bodies after the attackers left the village.
"They came to our village... and lied to us that they had come to preach to us and when almost all the villagers had gathered, another set of insurgents emerged from nowhere and opened fire on the congregation before we all scampered for safety."
Another survivor, Kallamu Bukar, said: "When we converged, another set of insurgents emerged from nowhere and joined those that were disguised as preachers.
"They opened fire on the congregation. The assailants also set ablaze several houses, shops and other personal effects."
The report came a day after witnesses said fighters had killed at least 200 civilians in three other villages in Gwoza district.
A community leader who witnessed the killings said that local residents had pleaded with the military to send soldiers to protect the area after they heard that the fighters were about to attack, but help did not arrive.
It took a few days for survivors to get word to Maiduguri because travel was dangerous and phone connections are poor, the AP news agency reported.
The killings earlier this week in Attagara, Agapalawa and Aganjara villages were confirmed by both Mohammed Ali Ndume, a senator representing Borno and whose hometown is Gwoza, and by a top security official in Maiduguri.
He insisted on anonymity, because he was not allowed to speak to the media.
Fighters from Boko Haram, which wants to establish Islamic law in Nigeria, have been taking over villages in the northeast, killing civilians and political leaders.
Thousands of people have died in its five-year-old campaign, more than 2,000 so far just this year, and an estimated 750,000 Nigerians have been driven from their homes.