The militants, a man and a woman, were in a motorised rickshaw stopped by a soldier on the outskirts of Borno state capital Maiduguri around 10:30 pm (2130 GMT) on Tuesday, an hour into the area’s night-time curfew.
“When they realised their cover was about to be blown they detonated the explosives they were carrying in the rickshaw, killing the soldier and themselves,” vigilante Babakura Kolo told AFP.
“It was evident they were on their way to launch suicide attack somewhere in the city but fortunately ran into a checkpoint,” he said.
Another vigilante, Umar Bulunkutu, said the soldiers’ suspicion was raised by the woman in the back seat, because “women are the ones Boko Haram uses for suicide attacks”.
“The soldiers wanted to know where they were going and why they were outside at that hour when all residents of the city were indoors in compliance with the curfew,” he said.
The vigilantes, who share information with the military, were clear when questioned by AFP that the occupants of the rickshaw were together and were both bombers.
Maiduguri has been under night curfew for some two years as part of security measures to curb deadly attacks in the city.
Hours earlier a girl believed to be as young as 12 killed six people and injured 47 when she detonated explosives outside a bus station in Damaturu, the capital of neighbouring Yobe state.
Boko Haram has stepped up its attacks since Nigeria’s new President Muhammadu Buhari was sworn in on May 29, vowing to crush the insurgency.
The wave of violence since the inauguration has claimed more than 1,000 lives, dealing a setback to a four-country offensive launched in February that had chalked up a number of victories against the hardline Islamists.
An 8,700-strong Multi-National Joint Task Force, drawing in Nigeria, Niger, Chad, Cameroon and Benin, is expected to deploy against the insurgents soon.