As Prime Minister Indira Gandhi repeatedly sounds the gloomy theme that war may break out in the Indian subcontinent, this country's hawks are intensifying pressures on her government to build a nuclear bomb.

These developments coincide with intelligence reports quoted in Washington that both India and Pakistan are engaged in construction projects at remote sites that could be used for nuclear explosions -- India's second and Pakistan's first.

Gandhi's concern over the possibility of war in the area, reiterated during the past two months in speeches and informal press conferences, and the push for India to develop nuclear weapons worry diplomats here, who admit they are unsure of their significance.

Both seem to have been sparked by fears of neighboring Pakistan's speedy development of an atomic bomb coupled with Reagan administration plans to bolster that country's military following the Soviet occupation of Afghanistan.

Gandhi told a partliamentary committee last Monday that she was worried that the U.S. arming of Pakistan "is creating a situation where everybody was drifting toward a war," according to a government press release on the closed-door meeting.

"The major danger was that, without anybody wanting it, suddenly there may be a war," she was quoted as telling the committee.

Gandhi also cited reports that Pakistan may set off a nuclear explosion some time between this July and September 1982 -- a time frame that many U.S. experts believe is too optimistic for Pakistan's clandestine atomic program.

Leading the pronuclear lobby, Girilal Jain, editor of the influential Times of India, wrote that India has little choice but to develop nuclear weapons "if we are to preserve our independence and integrity" in the face of Pakistan's bid to build atomic weapons and U.S. moves to sell it arms.

His April 11 editorial-page column has been followed by similar articles in important Indian papers and a report Tuesday in the Bombay Daily, a new tabloid, that India will test its first hydrogen bomb next month.

While the Bombay paper's report is discounted by diplomats here, many of whom say India does not have the capability to make a hydrogen bomb, the renewed calls for an Indian nuclear weapons program are taken seriously.

It is unclear just how influential the pronuclear lobby is with the Gandhi government. Its views are believed to strike a responsive cord with many Indians who have an emotional fear of attack by Pakistan, which is trying to develop atomic weapons, and China, which already has them. India has fought wars with both neighboring countries.

"The grim prospect before us, then, is that of nuclear blackmail from two powers peripheral to our territory, acting either independently or in collusion," retired Lt. Gen. M. L. Thapan wrote in an article in the Statesman Tuesday. He recommended that India reconsider its renunciation of nuclear weapons development.

Adding to the chorus, K. Subrahmanyam, director of the government-supported Institute for Defense Studies and Analysis, urged the government "to exercise the nuclear option" even before Pakistan conducts its test.

Gandhi repeatedly has said the India has no present plans for a second nuclear explosion, but she generally adds that the government would detonate one if it were in the national interest.

Although India is not believed to have embarked on a nuclear weapons program, few experts doubt its technical ability to do so.

Furthermore, there is a widespread belief here that India's reply to any nuclear blast by Pakistan would be a bigger one of its own.

One usually well-informed Western diplomat speculated that construction activity at Pokharan, the remote site in the Rajasthan Desert where India staged its 1974 nuclear explosion, is standby preparation for a second blast in case Pakistan detonates a nuclear explosion.

Gandhi's concerns about the possible onset of war in the region have been sounded from a variety of platforms.

While vague on the specifics of how the war would start and who would fight whom, her warnings all carry the same theme of an apparently inevitable march toward conflict because of Western and Soviet naval forces in the Indian Ocean, the Iranian-Iraqi war and American plans to arm Pakistan.

In February, Gandhi told Italy's largest newspaper, Corriere della Sera of Milan, that she is concerned about the "alarming signals of a major war" that might break out in Asia.

She told Parliament last month that the world situation is grimmer now than any time in the past two decades and warned that "powerful nations of America and Europe have a special flair to fight their wars on the soils of underdeveloped and developing countries."

In a response to British Prime Minister Margaret Thatcher's address to the Indian Parliament two weeks ago, Gandhi said, "The specter of the cold war peeping in our doorway causes us grave apprehension. We have already spoken to you about the dangers of giving sophisticated arms to Pakistan."

Official in Pakistan have accused Gandhi of trying to create "a war hysteria" through her remarks.

"These statements have created an atmosphere of artificial crisis in bilateral relations," Pakistani Foreign Minister Agha Shahi said April 17 as he was leaving for Washington for talks with the Reagan administration.

"It is regretted that India's obsession over a nonexistant military threat from Pakistan verges on the surreal and is the main source of complications in developing rational bilateral relations," he added.

Gandhi's political opponents also have criticized the prime minister for harping on the possibilities of war. Former defense minister Jagjivan Ram said there is no threat of war, and Janata Party leader Samarendra Kunda accused the prime minister of attempting to divert the nation's attention from domestic issues such as unemployment and inflation.