The attack in Borno state Wednesday was unleashed the same day as twin suicide bombings in Cameroon and a series of blasts at two bus stations in Nigeria that left at least 50 dead.
"The gunmen we believe to be from Boko Haram came into our village around 9 pm yesterday (Wednesday) and shot dead eight people," said Umar Goni, a resident of Pompomari village.
The militants stormed the home of the village chief who was away at the time but killed his son before moving on to other houses where they killed a vigilante and people who had been displaced by previous attacks, Goni said.
Pompomari is about 15 kilometres (nine miles) from Biu, the biggest town in southern Borno, the state which has borne the brunt of the Boko Haram insurgency.
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Buhari took office in May vowing to crush the insurgency but since then more than 750 people have been killed, according to an AFP count.
The bloodshed came after Boko Haram released a new video on Twitter, maintaining they were not defeated and vowing: "We will be coming from where you never expected, stronger than before."