Terror outfit Jaish-e-Mohammad on Tuesday allegedly threatened to blow up major railway stations and places of religious and tourist interest in Uttarakhand in retaliation to the hanging of Parliament attack convict Afzal Guru, a senior police official said.

The letter written purportedly by the Karachi based area commander of terror outrfit Jaish-e-Mohammad contains a threat to blow up Dehradun, Haridwar and Kath Godam rail junctions near Nainital and prominent places of religious and tourist interest like Har Ki Pauri in the holy city, Haridwar SSP Arun Mohan Joshi said.

"Though the authenticity of the threat and the origin of the letter is being examined, we are not taking any chances and have alerted the highest authorities in places mentioned in the letter", he said.

Security around the places mentioned in the letter has been beefed up.

The letter addressed to former superintendent of Haridwar Railway station Amrinder Singh was received on Tuesday, he said adding similar letters have been issued to retired railway officials in the past as well.

The difference between the latest threat letter and those received in the past is that this one has purportedly been written by Jaish-e-Mohommad whereas the earlier ones bore the name of Lashkar-e-Toiba, the SSP said.