A bomb device exploded in Quetta bound Akbar Bugti Express when the train left Dera Allahyar railway station.
According to reports the bomb device planted at the track was detonated causing derailment of three bogies of the train, which was carrying passengers from Lahore to Quetta.
The train avoided a major disaster due to its slower speed, the railway authorities said.
The bomb device detonated with remote control carrying 15 to 20 kilograms explosives, police said.
Heavy contingents of security forces and police reached to the spot of the bombing after the incident.
The blast damaged 15 feet portion of the railway track causing suspension of the railway traffic, officials said.