Security sources said the convoy of forces was going past the Tirzai area when the remote-controlled improvised explosive device went off. Resultantly, one soldier died and two others injured.
The forces cordoned off the area and moved the injured and the dead to hospital.
Pakistani troops in June last year began a long-awaited drive to clear insurgent bases in the district after a bloody attack by the Taliban on Karachi airport sank faltering peace hopes.
The army has intensified its offensive since the Taliban’s massacre of 153 people, 134 of them children, in a school in Peshawar last December.