Updated

Witnesses say three suicide bombers have exploded at a checkpoint in Nigeria's northeastern town of Madagali, killing two self-defense fighters who challenged them.

Friday's attack is blamed on Boko Haram Islamic extremists. It came as scores of people were being searched before the weekly market of vegetables, meat and livestock.

Last week, three girl suicide bombers were killed on the outskirts of the same town. In December, two women suicide bombers killed 57 people and wounded 177, including 120 children, at Madagali market.

Resident David Abawu says Friday's attackers blew themselves up when self-defense fighters wanted to search them.

Nigeria's military and civilian fighters who work with them have intercepted many suicide bombers in recent months, preventing much higher death tolls.