It was reported that other people were wounded while some are still missing in the assault on Saturday evening in the village of Toumour in the Diffa region.
Witnesses and other officials confirmed the attack, which came hours before municipal and regional elections went ahead across the country on Sunday.
“Some victims were killed or wounded by bullets, others were burnt inside their houses, consumed by the flames of an enormous fire set by the attackers,” said a local official.
Between 800 and 1,000 houses, the central market and numerous vehicles were also destroyed in the fire, he added.
Roughly 70 attackers arrived at Toumour at around 1745 GMT on foot, having swum across Lake Chad, said the official. The attack itself lasted three hours.
“They first attacked the residence of the traditional chief, who only just managed to escape,” he said.
“It was an attack of unprecedented savagery,” said a local elected official who asked not to be named.
“Nearly 60 percent of the village has been destroyed.”