State governor says soldiers are working to locate and free 333 schoolboys abducted by armed men.
The Boko Haram armed group has claimed responsibility for the weekend attack on a village in Niger that left at least 27 dead.
More people were wounded and some reported missing in the assault on Saturday evening on Toumour in the Diffa region, said a senior local official on Monday.
Witnesses and other officials confirmed the attack, which came hours before municipal and regional elections were held across Niger on Sunday.
“We hereby inform the world that we are responsible for the attack in the town of Diffa in Niger Republic yesterday [Saturday],” said a three-minute video sent to AFP news agency.
The footage showed a fighter in military camouflage and his face swathed in a turban, speaking in Hausa, which is widely spoken in the region.
“We carried out the attack with the power of Allah and His help,” it said.
The group, led by elusive leader Abubakar Shekau, said more Christians could be attacked ahead of Christmas.
Local officials said some of the victims in Diffa were shot and others burned to death inside their homes.
Between 800 and 1,000 houses, the central market and numerous vehicles were also destroyed in the fire set by the attackers, they said.
Dozens of attackers arrived at Toumour on foot in the evening, having swum across Lake Chad, said one official.
The attack lasted three hours. “They first attacked the residence of the traditional chief, who only just managed to escape,” the official said.
“It was an attack of unprecedented savagery,” said an elected local official who asked not to be named. “Nearly 60 percent of the village has been destroyed.”
Attacks by Boko Haram began in 2009 in northeastern Nigeria before spreading to neighbouring Niger, Cameroon and Chad.
Since then, more than 36,000 people have been killed in Nigeria and two million forced to flee their homes, sparking a humanitarian crisis in the region.
A regional military coalition has been formed to fight the group.