Indian nuclear installations are under "very serious threat" from a Pakistan-based militant group, which may be planning a major attack, a top Indian official said.

National Security Adviser M.K. Narayanan issued his warning Friday as an Indian army official said a Pakistani army major was among three suspected Islamic militants killed days ago by security forces in Indian-controlled Kashmir.

Islamabad dismissed both accusations, calling them Indian efforts to defame Pakistan.

But the allegations could further damage the badly strained peace process between the two South Asian nuclear rivals, whose relations have suffered since more than 200 people were killed and 800 injured in July 11 bombings on the Bombay train network.

India has blamed the Bombay attacks on Lashkar-e-Tayyaba, the Pakistan-based militant group that Narayanan said is a threat to India's nuclear facilities.

"We have at least two or three serious threats ... there is information that maybe one of our atomic installations could be the target," Narayanan said in an interview with private television news channel CNN-IBN. "It's an LeT operation ... it is a very serious threat."

Pakistan's Foreign Ministry derided Narayanan's comments.

"These allegations are simply an effort to malign Pakistan," Foreign Ministry spokeswoman Tasnim Aslam said.

The India-Pakistan peace process has stalled since the Bombay blasts, which Prime Minister Manmohan Singh has said were "instigated, inspired and supported by elements across the border" — a clear reference to Pakistan and militants based there.

Pakistan has denied any knowledge or involvement in the blasts.

But the allegation of a Pakistani soldier among suspected militants could worsen the diplomatic situation.

Lt. Col. V.K. Batra, an Indian army spokesman, told reporters that "intelligence and documents" recovered from the dead man's body identified him as Pakistani Maj. Mohammed Haider, serving in the 9 Baloch Regiment.

He and two other suspected insurgents were killed Tuesday during a gunbattle with Indian security forces after the three crossed over from Pakistani-controlled Kashmir, Batra said in Srinagar, the main city in Indian Kashmir.

That battle was near the Line of Control, the de facto border which divides Kashmir between India and Pakistan, about 85 miles north of Srinagar, the main city in Indian Kashmir.

India has long accused Pakistan of providing aid and training to the Kashmiri militants — an accusation that Pakistan denies.

On Friday, Islamabad scorned Batra's allegations.

"It is absurd and a concocted story aimed at tarnishing the image of Pakistan," said Pakistan army spokesman Maj. Gen. Shaukat Sultan. He said India had not used the hotline, which links the two countries' military officials, to discuss the issue.

India and Pakistan have fought three wars, two of them over control of Kashmir, since they became independent from Britain in 1947.

Nearly a dozen Islamic rebel groups have been fighting Indian forces to seek Kashmir's independence from India or its merger with Pakistan since 1989. More than 68,000 people have been killed in the conflict.