One soldier was killed and three others were injured after suspected militants fired at an army convoy in Assam's Tinsukia district on Saturday, defence officials said.The incident took place at around 5.30 a.m., in the Pengeri area, Defence public relations officer Lt. Col. Suneet Newton said."They (the militants) had planted an improvised explosive device (IED) on the road. When the IED exploded, the convoy stopped. Then the militants fired indiscriminately," Newton said, adding that although the forces retaliated, four soldiers were injured of which one succumbed in the hospital.Locals said that the militants had fired upon the vehicle from both side of the road, which are forested areas.On Wednesday, militants attacked a van of the Pengeri tea estate killing one person and injuring two others.