The government of Prime Minister Indira Gandhi, stung by allegations that it callously ignored urgent police warnings that massacres were imminent in the far northeastern state of Assam in February, today bitterly accused its critics of "unpatriotic and seditious" behavior.

A prominent Indian investigative reporter triggered the controversy by publishing a magazine article disclosing that local police in Assam repeatedly had sent cables warning of massacres weeks before 3,600 people were killed in communal clashes. The opposition in Parliament subsequently accused Gandhi of going ahead with the state election that prompted the violence solely out of political expediency.

The Assam massacres occurred in a burst of accumulated rage that had grown during a three-year campaign by indigenous Hindu Assamese to strike nearly 4 million mostly-Moslem immigrants from Bangladesh from the electoral rolls and expel nearly a million of them to surrounding Indian states.

In the worst communal violence since the Hindu-Moslem carnage that accompanied partition of British India in 1947, scores of villages in Assam were wiped out and more than 300,000 persons were left homeless.

In an emotional statement to the Indian Parliament, Home Minister P. C. Sethi today acknowledged the existence of police cables warning of impending disaster in Assam. But he called the Indian press' interpretation of them "perverse" and said that opposition attempts to blame the government for the Assam tragedy disregards "national interest."

C. M. Stephen, a general secretary of the ruling Congress (I) Party and effectively a government spokesman, called the disclosures "unpatriotic and seditious" and said the opposition maliciously had slandered the government at a time of crisis.

The government leaders called for "reconciliation and healing" in Assam instead of recriminations.

Arun Shourie, a prize-winning investigative reporter and former editor of the Indian Express newspaper, published in the India Today magazine what were purported to be government cables that warned of the Assam massacres weeks before they occurred.

A Jan. 16 police "situation communication" cited by the magazine warned a month before the massacres that a linkup between the fundamentalist Hindu organization, the Rashtriya Swyamsewak Sang, and election opponents of the All-Assam Students Union could lead to a "communal conflagration . . . just prior to or immediately after the election." Most of the massacres occurred around the polling dates in the election, which ended Feb. 21.

The magazine reproduced another dispatch sent by a police inspector general to Assam district headquarters on Jan. 25--more than three weeks before the Feb. 18 massacres that left 1,383 dead in the vicinity of the town of Nellie--which warned that opponents to the elections "may plunge the state into a communal turmoil by resorting to large-scale violence, arson, looting, murder, etc."

The most dramatic disclosure was of an urgent cable reportedly sent three days before the Nellie massacres by the officer in charge of the Nowgang district police station to a police battalion commander's headquarters six miles away, saying, "Information received that last night about 1,000 Assamese of surrounding villages of Nellie with deadly weapons assembled at Nellie by beating drums. Minority peoples are in panic and apprehending attack at any moment. Submission for immediate action to maintain peace."

By all accounts from Assam, no police action was taken before a mob of Assamese wielding bows and arrows and machetes set out at 5 a.m. on Feb. 18, marching to Nellie to the beat of primitive drums and swelling along the way to 12,000 persons. The massacre began at 8 a.m. and continued for at least four hours.

Sethi told Parliament that the published cables had proved that the state government had been prompt in alerting local police about the need for action.

The India Today investigation into the events leading up to the Assam massacres was the most thorough done to date. Foreign journalists have long been forbidden to enter Assam or any part of India's strategically sensitive far northeastern region. The government's suspicion of foreigners in the far northeast stems partly from the area's proximity to China and partly from a sensitivity to ongoing insurgencies in the region, which Gandhi has frequently linked to an unspecified "foreign hand."

Opposition leaders in Parliament have seized upon the published police cables to charge Gandhi with callously insisting that the election be held out of concern for her own political fortunes despite clear warnings that it could trigger violence. They claim that Gandhi wanted the vote because she was certain to win a majority that she felt she needed after her Congress (I) Party had sustained defeats in two southern states.

The prime minister repeatedly has said that cancelling the balloting was unthinkable because it would have encouraged forces of regionalism in the northwestern Punjab state and elsewhere in India.

Critics also have alleged that the greatly beefed-up Assam security forces, including 8,000 officers airlifted to the state, were deployed solely to protect polling officials and candidates and not to ensure the safety of the threatened immigrants.

The debate over the government's handling of Assam has taken on added importance because of a resurgence of communal violence in the Punjab following the murder last week in Amritsar of a police deputy inspector general who had been investigating Sikh extremists. The police officer was shot just outside the Golden Temple, Sikhism's holiest shrine, and his assailants are believed to have taken sanctuary in the temple complex.

A wave of arson and Sikh-Hindu clashes has swept through the southern Punjab city of Patiala, resulting in the imposition of an around-the-clock curfew there, and the Army has been put on the alert throughout the state.