The blast derailed coaches of the Khushhal Khan Khattak Express train, two of which were overturned, according to Chief Controller Railway Station Naseem Ahmed Doger.
The train was reportedly travelling at 60-70km per hour from Peshawar to Karachi when the explosion occurred.
General Manager of Pakistan Railways said the oil tank of the train was also damaged due to the explosion.
A large crater has formed under the track, making rescue efforts difficult.