The Indian Air Force has denied the television report about the IAF being infiltrated by Lashkar-e-Tayiba cadres, but Air Chief Marshal S P Tyagi has, sources said, ordered a probe into the matter.

The story, which was aired by the Times Now television channel on Friday, claims that a letter written on November 30, 2005 by National Security Advisor M K Narayanan warns state chief secretaries, intelligence and police officials about the possibility of jihadis entering the air force, army and navy.

The Prime Minister's Office has also asked the Intelligence Bureau to investigate how a confidential letter, with repurcussions on national security, could have been leaked to the media and by whom.

"We are always on alert and our counter-intelligence wings continuously monitor every officer. Their credentials are always being checked and those persons with doubtful integrity are immediately weeded out. This story is nothing but a figment of the imagination of some scribes," Wing Commander Mahesh Upasni told rediff.com late Friday night.

According to the Times Now report, M K Narayanan had written a 40-page letter, in which he pointed to the intrusion by jihadis in the Indian Air Force.

"I do not know whether they are talking about Kashmiri jihadis or non-Kashmiris, but the Indian Air Force is always on alert. We keep doing such exercises on a regular basis. The nation should rest assured that the interests of the country are safe in the hands of the Indian Air Force, the army and navy," Wing Commander Upasni added.

Reacting to the report, Arun Bhagat, former director, Intelligence Bureau, said between last November and July, the IAF would have cleaned up any infiltration.

Arun Jaitley, the Bharatiya Janata Party spokesperson, demanded that the government issue a statement on the issue. "We would like to know the facts from the government and what it intends to do. The government must change its mindset and strengthen our intelligence network," he said.

The government, for its part, has maintained a studied silence on the matter.