A threat letter allegedly from banned terrorist outfit Indian Mujahideen to a leading residential school here has triggered fear among parents, some of whom have begun to take home their wards staying in hostels of prominent boarding schools in the city.

The letter, purportedly sent by the terror outfit, was found outside the residence of the principal of Welham Girls' School, one of the top residential schools in the country, on Saturday evening.

The letter addressed to the school principal and threatening to "avenge what happened with Muslims in Kashmir, Gujarat and Muzaffarnagar" has led to a sense of insecurity among parents.

Some of them have started taking home their wards staying in the hostels of prominent boarding schools for some time, at least till the threat perception is there, sources said.

However, authorities at different boarding schools claimed the situation was normal and majority of the students were still at the hostels. Welham Girls' School administration, in an email to parents, said there was no reason to panic, but offered them the option of taking their wards home for the time being if they felt insecure.

Meanwhile, security around eminent residential schools in the city, including Welham Girls, Welham Boys and the Doon School as well as other important places, has been tightened to deal with any eventuality, Dehradun SSP Ajay Rautela said.

Every aspect of the letter written in Hindi with quite a few Urdu words in it, is being examined minutely, he said.

The letter, written allegedly by an IM commander, had threatened to avenge what happened with Muslims in Kashmir, Gujarat and Muzaffarnagar, between March 30 and April 8.

However, it does not specify what exactly would be done and which places would be targeted, Rautela said.