The pipe-smoking former diplomat, born in 1936, was a central figure in the Congress-led coalition government that took power last May and had an illustrious diplomatic career.

Paying tribute to Dixit, seen as a main architect of India's foreign policy in the era after the Cold War, Prime Minister Manmohan Singh described him as a "close friend" and a "wise strategist."

"The nation has lost a true patriot, a great diplomat and a wise strategist," the prime minister said.

Dixit was pulled out of retirement after Congress won election to serve as national security advisor.

Prime Minister Khaleda Zia also yesterday expressed her deep shock and grief at the sudden demise of Dixit.

"I am deeply saddened to know about the passing away of Mr. JN Dixit, National Security Adviser to your Excellency," Khaleda said in a message of condolence to her Indian counterpart.

She said Bangladesh recalls the immense contributions of Dixit to strengthening the Bangladesh-India bilateral relations during his assignment in Dhaka in the 1970s, and more recently in his capacity as the National Security Adviser.

Dixit, who wrote a number of books, was a prime mover in pushing forward a nascent peace process with longtime rival Pakistan where he earlier served as India's high commissioner.

He was also involved in ongoing border negotiations with China.

Before his retirement as foreign secretary a decade ago, he had also served as ambassador or high commissioner to Afghanistan, Sri Lanka and Bangladesh.

Former colleagues G. Parthasarthy and Muchkund Dubey described him as a brilliant diplomat.

One of India's top nuclear scientists, Anil Kakodkar, called Dixit's death a "big loss to the country."

"Dixit had been a strong support to our nuclear programmes. He was very knowledgeable and knew all the nuances of foreign affairs," Kakodkar, chairman of India's Atomic Energy Regulatory Board, said.

Dixit played a vital role in steering India's foreign policy in the early 1990s soon after the collapse of the former Soviet Union, New Delhi's longstanding friend and Cold War ally. (AFP/BSS)