"Boko Haram needs to make sure that local communities do not support government, and they're using violence to try and further that aim," he said.
Among their latest targets are young people who do not join their rebellion. Scores of school and college students have been killed and dozens of schools forced to close in a region of the country that already suffers the worst poverty and literacy rates.
In Mbitiku, a village of mud huts, a primary school and a few concrete buildings, the businessman said 30 fighters marched in carrying large guns. They slit the throats of 10 young men, he said, so the sound of gunfire wouldn't scare off other potential victims. Cutting throats the Muslim method for slaughtering animals also signals disdain for the victims.
As the insurgents left the town they burned several houses to the ground, the businessman said.
Mbitiku is about 100 kilometers (60 miles) southeast of Maiduguri, the Borno state capital that is the birthplace of Boko Haram, near the border with Cameroon in an area where insurgents are using mountain caves as hideouts.
Boko Haram has killed thousands of people in the past four years in a bid to force Nigeria, Africa's most populous nation, to adopt the group's harsh version of Islamic law. Three northeastern states, including Adamawa, have been under emergency rule for six months and the United States now classifies Boko Haram as a foreign terrorist organization.
Thursday night, suspected Boko Haram fighters struck at the heart of Adamawa, killing three young men at the popular Kasuwar Gwari market in the state capital, Yola.
Witnesses said the three belonged to a vigilante group that had been helping soldiers flush out insurgents.
"The attackers stormed the market, fingered their victims and shot them at close range," said Musa Aboki, who sells oranges.
Several villages in Adamawa state have been attacked in recent weeks and families that can are moving to the cities for safety, said the businessman. But most rural people are subsistence farmers growing corn and rice and have no choice but to remain at home despite the danger, he added.
The United Nations has documented some 10,000 people fleeing northeast Nigeria to neighboring Chad, Cameroon and Niger in recent months but says the numbers are probably much larger. Many more are displaced inside the West African nation. Tens of thousands of farmers have abandoned their fields.
Mbitiku residents said that before the attacks, police had closed their local posts to make villages less tempting a target. Boko Haram fighters, they said, are often better armed than security forces.
Soldiers have moved back into the Adamawa countryside since the Mbitiku attack, they added.
The businessman said he still runs his shop in the village by day, selling items like soap and flashlights, but he hides in a government building at night. He has sent his wife and three children to a nearby town for safety.
Civilians in Borno and Yobe states, also under emergency rule, have formed vigilante groups that patrol neighborhoods armed with machetes, clubs and knives and arrest suspects they hand over to security forces. Authorities have praised the groups, calling them "heroes." Adamawa has not formed its own vigilante groups amid threats from extremists to attack villages that do. But civilian volunteers from other states have come to man checkpoints and are housed by soldiers.
Police say they are investigating reports that vigilantes hunting Boko Haram in Borno state killed eight herdsmen in early November, mistaking them for insurgents.
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Associated Press writers Haruna Umar in Maiduguri, Nigeria, and Michelle Faul in Lagos, Nigeria, contributed to this report. Murdock reported from Lagos.
