Soldiers in Nigeria have shot dead a civilian and three police officers who were transporting a suspected criminal.The police say the officers were taking a man believed to be behind several kidnappings to a police station in the north-eastern Taraba state.The troops fired at the undercover police because they mistook them for kidnappers, according to the military.The police say the soldiers released the handcuffed suspect, who is on the run. Four other people were injured.Soldiers were not aware of a covert police operation in the area so they took notice when a member of the public made a distress call about suspected kidnappers, the military said in a statement.The undercover police then refused to stop at three military checkpoints which prompted a "hot pursuit", according to the statement. One of the wounded then told the soldiers they were undercover policemen.The military described it as a case of mistaken identity.The police, however, said the officers were shot at several times by the soldiers "despite sufficient proof that they [were] police personnel on legitimate duty".After the shooting, the soldiers released the handcuffed suspect, according to the police, who named him as Alhaji Hamisu, allegedly a "notorious kidnap kingpin" involved in high-profile kidnaps.The police have opened an investigation into what they call a "bizarre and unfortunate" incident.