Two suspected members of Nigerian Islamist sect Boko Haram were killed Saturday when an explosive they tried to throw at policemen at a checkpoint went off in the flashpoint city of Kano, police said.

The blast happened days after a suicide attack Monday at a bus station in Kano, the most populous city in northern Nigeria, that killed at least 41 people and injured 65 others, according to a rescue official. Kano state police boss Musa Daura said four accomplices of the victims of Saturday's blast were arrested afterwards.

"Two suspected members of Boko Haram were killed by an explosive they were trying to haul at a police checkpoint in Hotoro area of the city," he told AFP. Three policemen were injured in the blast, Daura said, without giving further details. One of the victims pretended to be a water vendor pushing a cart, hiding the explosive in a load of jerry cans, he said.

The man threw the device, which mistakenly hit his accomplice, who was pushing his motorcycle through the checkpoint beside the cart, the police boss said.

It exploded and killed both, he said. Four suspected accomplices, including two Niger nationals, who were hiding nearby with a plan to seize policemen's guns after the blast, were arrested, he added. Minutes before the blast, another explosion went off at a nearby checkpoint but no one was injured, he said. Violence linked to Boko Haram's insurgency in northern and central Nigeria, including killings by security forces, has left some 3,000 people dead since 2009. The sect's deadliest assault yet occurred in Kano in January last year, when at least 185 people were killed in coordinated bomb and gun attacks.