The insurgents attacked the farmers on Sunday as they were harvesting crops in Moranti outside Maiduguri, the capital of Borno state, two sources said.
“The attackers used knives, not guns, to kill all eight farmers, so as not to attract attention,” militia leader Babakura Kolo said.
Local communities have resorted to armed vigilantes or militias, who work alongside the army, as self-defence.x
“They (Boko Haram) hacked the farmers and slit their throats,” said a second militia leader, Umar Ari, who was involved in evacuating the bodies.
Boko Haram militants slaughtered 14 farmers earlier this month as they worked on fields in Ngwom village near Maiduguri.
Meanwhile, a Boko Haram rival group, the Islamic State West Africa Province (ISWAP), launched attacks at the weekend on three military bases in Borno and neighbouring Yobe state that were thwarted by troops, according to security sources and residents.
ISWAP claimed to have killed a dozen soldiers, but this could not be independently verified.
At least 36,000 people have been killed and around two million people have fled their homes since Boko Haram launched its insurgency in 2009.
The violence has spread into neighbouring Niger, Chad and Cameroon and prompted the creation of a regional military coalition to fight the militants.