Five suicide bombers trying to infiltrate Nigeria's northeastern city of Maiduguri have died in explosions that killed at least three civilians. Police say the two attacks Sunday night are blamed on Boko Haram Islamic extremists.<br/><br/>Deputy Superintendent Victory Isuku says three men wearing vests with explosives approached a military checkpoint while shooting. He said one exploded, killing all three and a civilian self-defense fighter.<br/><br/>Two hours later, two female bombers blew up, killing themselves and two unidentified people.