Kolkata: Passengers of the New Delhi- Dibrugarh Rajdhani Express had a miraculous escape early this morning when a powerful bomb exploded on the railway tracks in central Assam just after the train passed the spot of the blast.

The train's air-conditioning machine and a water tank was damaged in the blast that occurred on a bridge over Dharani river between Diphu and Doldolni in the Lamding division of NF Railway at 12.50 am, North-east Frontier Railway sources said.

There was no injury or casualty in the blast.

Hearing a loud blast and feeling a jerk, the driver and guard stopped the train and saw that the AC undergear and the water tank of a three tier coach damaged, they said.

The Rajdhani Express later continued its journey.

About 1.5 metre portion of the track on the concrete bridge was damaged. Police rushed to the spot and gave security clearance at 4 am for starting repair work on tracks.

Railway officials were assessing the damage for repair and restoration of the track.

Trains passing over the track have been halted at Dimapur, Diphu, Lamding and other stations, the sources said.

The identity of those behind the blast was not clear.

Atleast 17 persons were killed and 11 injured in a series of attacks by ULFA militants in Assam's Tinsukia and Dibrugarh districts yesterday.