Decomposed bodies of more than 70 people, many with their throats slit, and a decapitated one, were discovered in what is believed to have been the execution site of the Nigerian Islamist group Boko Haram.
Soldiers from Niger and Chad who liberated the Nigerian town of Damasak saw the bodies strewn under the concrete bridge on one of the roads leading out of the town.
Among the dead was the imam of the town.
Many of the bodies were in a state indicating that the killings took place many days ago.
Damasak was seized by the Islamist group in November. Most of the residents had fled the town leaving behind the old and the sick.
The soldiers will stay in the town, which lies close to the border with Niger, until Nigerian troops arrived.
What is Boko Haram?
Boko Haram, a fundamentalist group, aims to impose its version of Sharia law in Nigeria. The group declared an Islamic caliphate in Gwoza, along the Cameroon border, in August 2014.
Boko Haram has raided several cities in the north of the country in a bid to take control of more land.
Three states, Adamawa, Borno and Yobe, have been under a state of emergency since May 2013, due to Boko Haram's deadly attacks.
The recapture of Damasak follows a regional offensive launched this year with Chad, Niger and Cameroon joining hands with Nigeria.
The Nigerian military claims to have driven the group out of all its pockets except in three districts.
But the retreating Islamists continued their killing spree in the town of Gamburu, on the border with Cameroon. At least ten were killed on 19 March.
As Nigeria prepares for presidential elections on 28 March, President Goodluck Jonathan, who is standing for re-election, told the media that Boko Haram had been mostly routed and that it would take no more than a month to recover the remaining territories from the group.
Boko Haram has killed thousands in a six-year insurgency aimed at establishing an Islamic caliphate in northeast Nigeria.