Suspected Boko Haram militants have killed at least 45 people in a village in Borno state, north-east Nigeria, witnesses have said.
The gunmen who stormed Njaba targeted men and boys before setting the village on fire, survivors added.
The raid happened early on Tuesday but was not reported immediately because of the remoteness of the area.
Boko Haram has killed thousands of people in its drive to establish an Islamic state.
Many survivors of the attack on Njaba fled to the nearby town of Damboa.
A resident of the town told the BBC the dead had been left to decompose because the villagers feared returning to Njaba.
The total number of dead remains unclear, with some reports suggesting the figure may be as high as 100.
Information often travels slowly from regions where Boko Haram is active, partly because the militants have damaged communications infrastructure.
Njaba is about 100km (62 miles) south of the state capital, Maiduguri. There were no security forces in the village at the time of the attack.
Many villagers were attending morning prayers when the attack happened, a witness quoted by news website Sahara Reporters said.
Fatima Abaka said there was "pandemonium" when the shooting started.
"I ran into the bush. Since then I [have] never seen my husband and three children," she said. "[I] came back to our village in the afternoon, dead bodies were scattered everywhere."
Another witness, Aminatu Mommodu, said the bodies of victims, including many men with their throats slit, were in the mosque.
Other villagers caught by the gunmen outside the mosque had been shot, she said.
Ibrahim Wagu, a Maiduguri resident who comes from Njaba, told Reuters news agency that two of his relatives had been killed.
"My older brother and my sister's first son were killed," he said.
Boko Haram controls large areas of Borno state but in recent months has also carried out cross-border raids into Chad, Cameroon and Niger.
The three countries have joined Nigeria to form a military coalition, which has recaptured several towns and villages in recent weeks.
Chadian forces have recently helped the Nigerian army recapture several towns and villages from Boko Haram.