Suspected members of a radical Muslim sect killed three people in a van blast near a military checkpoint, a Nigerian official said Tuesday, the latest in an escalating series of attacks in the country's restive northeast. Maj. Gen. Jack Nwachukwu Nwaogbo, the commander of the Joint Military Taskforce, said an explosive went off under the van Monday evening as its driver slowed down at a military and police checkpoint in the city of Maiduguri. The blast killed the driver and two passengers. Authorities blame a radical Muslim sect locally known as Boko Haram for the bombing, one of many attacks that have targeted security officers, local leaders and clerics in and around Maiduguri over the last year.