A second day of terrorist bombings in the Indian capital and in adjoining states brought the death toll to 72 today, and Army troops began patrolling parts of the city.

Police raided about a dozen Sikh temples looking for separatist guerrillas who launched an unprecedented wave of random terror yesterday by leaving explosives-packed portable radios in public places.

More than 200 Sikhs suspected in the bombings were reported rounded up here, and at least 500 were arrested in the embattled state of Punjab in the wake of an intricately coordinated series of bombings in the Indian capital and the adjacent states of Haryana, Uttar Pradesh and Rajasthan. A total of 730 arrests have been made nationwide.

The continuing crisis is the worst that Prime Minister Rajiv Gandhi has faced since Hindu reprisals against Sikhs following the assassination of his mother and predecessor, Indira Gandhi, by Sikh bodyguards on Oct. 31. More than 1,000 persons died in that crisis.

The prime minister called an emergency Cabinet meeting today to discuss the crisis with senior ministers. His government warned that the "sternest measures" would be taken to restore order, and it appealed for public calm.

Eleven persons died in 19 bombings in the capital alone today, where police defused five unexploded bombs. Forty of the 72 persons killed in the two days of bombings died in New Delhi, where 109 also were injured. Thirty bombs have exploded nationwide during the past 24 hours.

The randomness of the bombings appeared to be calculated to grip the capital in terror and, presumably, lead to widespread civil disorder that would undermine the government's efforts to draw moderate Sikhs into talks for a negotiated settlement to demands for increased autonomy for Punjab.

Home Affairs Minister S.B. Chavan, in a television broadcast tonight, blamed the bombings on "antinational elements who do not wish the political process to begin for the solution of the Punjab problem." Security officials said they feared more booby-trapped portable radios had been planted in the capital and elsewhere.

The military-like precision of the terror campaign appeared to confirm government officials' fears that the infrastructure and chain of command of the Sikh extremist movement -- thrown into disarray last June by an Army assault on the Sikh Golden Temple complex at Amritsar -- had been restored underground.

Separatist guerrilla leader Jarnail Singh Bhindranwale, a fundamentalist preacher, and his top political and military aides were killed in the raid on the Sikhs' most holy shrine, and hundreds of separatists were arrested in a statewide crackdown that followed.

Although government spokesmen claimed at the time that the Army sweep had "broken the back" of the terrorist movement, security sources have been warning in recent weeks that separatist guerrillas had been regrouping in secret training camps just across the border in Pakistan, and were training for a wave of attacks under new leadership.

India's leading Sikh historian, Kushwant Singh, who is a member of Parliament, said today that he had received information recently from Punjab that Pakistani Moslems had infiltrated the separatist underground movement and were helping to organize a large terror campaign that they expected would result in a Hindu backlash against Sikhs and further destabilize India.

Pakistani officials consistently have denied Indian allegations of cross-border training camps, noting that any involvement by Pakistani nationals was limited to bands of smugglers who long have penetrated the porous frontier in both directions with shipments of arms and other goods.

The government's attempts to reach a negotiated settlement with moderate Sikhs suffered an additional setback today when Harchand Singh Longowal, president of the Akali Dal, the mainstream Sikh political party, announced his resignation, apparently as a direct consequence of the bombing wave.

Longowal said that he had been seeking a peaceful solution to the Punjab crisis but that others had conspired to foment violence and undermine negotiations with the goverment.

Longowal, a relative moderate, had been challenged last week by Joginder Singh, the father of Bhindranwale.

The first series of explosives-packed transistor radios that detonated almost simultaneously at about 7 p.m. yesterday in bus terminals and other public transportation depots apparently was triggered by timing devices. But other explosions later in the evening and this morning appeared to have involved booby-trap devices set off when the victims found the radios and attempted to turn them on.

In one such case today, a 25-year-old fish peddler in south Delhi's Chittaranjan Park left his slum hut at 7 a.m. and discovered a three-band portable radio lying on the ground, police said. Authorities said the peddler rushed back into the hut to show it to his wife and three children, and when he switched on the radio, it exploded, killing all five.

In other cases, bomb-laden portable radios were left on buses and trains or, according to police officials, were handed to children, who took them home.

Police repeatedly issued public appeals to stay away from suspicious-looking objects, particularly transistor radios lying unattended. But millions of illiterate slum dwellers had virtually no access to the warnings, and the authorities said they feared there still might be undiscovered radio bombs.

Asked whether they expected a wave of reprisal attacks, some Sikhs recalled that nearly 36 hours had passed after the assassination of Indira Gandhi before Hindu mobs began attacking Sikhs in some of the worst sectarian violence since partition of the Subcontinent into Hindu India and Moslem Pakistan in 1947.

The Sikh owner of a glass factory, interviewed at the Bangla Sahib temple here, said that he expected reprisal attacks to be on a "small scale" unless right-wing Hindu groups and political parties organize mob violence. "In either case, Sikhs will defend themselves this time. We will fight to the death," said the businessman, who asked that his name be withheld.

Kushwant Singh, who during the November anti-Sikh riots sought sanctuary on the Swedish Embassy compound, said in an interview, "There may be a kind of shock still settling in. When they the Hindus recover from the shock, it could come tomorrow or the next day. It's still in the cards. I don't think it's over."

Leaders of several Hindu organizations blamed the government for failing to control Sikh terrorism and said that an emergency meeting of the Hindu Forum, an umbrella organization of 250 Hindu groups, was being called for Sunday.