The Indian Air Force has said the 'mysterious blast sound' heard in Ahmedabad, Gandhinagar and Vadodra districts of Gujarat on Monday morning was 'sonic boom' of a low-flying fighter plane.

Earlier report: 'Mysterious blast' heard in Gujarat

IAF spokesperson T K Singha said it was a 'planned profile' by the IAF and there was no reason for panic.

"One MiG-21 fighter jet was conducting a planned profile low flight from one of the bases in South West Air Command at 13 km above sea level," Singha said.

He said a change in atmospheric pressure pattern was formed when the jet entered the supersonic (speed of sound) stage resulting in a blast-like sound.

Singha said the same sound will be heard again when the jet returns to subsonic speed.

The spokesman said it was not surprising that the sound was heard across the state as sonic boom can be heard for hundreds of kilometres.