Adamsi Tar said the suspected militants had attacked a village about 15 kilometres from Chibok in volatile northeastern Nigeria, burning several homes and looting food.
As the assailants tried to flee, vigilante members opened fire on them, killing eight. One was arrested and the rest fled, said Tar, the local leader of the vigilante group.
"The gunmen fired shots indiscriminately because they had no idea where the shooting was coming from. When they realised their response was futile they retreated," he said.
Boko Haram fighters kidnapped 276 girls from the remote town of Chibok on April 14, leading to global outrage. A total of 219 are still missing.