In an unprecedented collective challenge to government attempts to curb press freedom, most of India's 10,000 newspapers shut down today to protest a draconian antipress measure adopted in Bihar, the nation's second most populous state, and tacitly supported by Prime Minister Indira Gandhi.

Journalists throughout the country walked out of their newspapers to protest what they regard as "creeping" state censorship reminiscent of the tough emergency regulations imposed by Gandhi between 1975 and 1977.

With the exception of The National Herald, the organ of Gandhi's Congress-I Party, all papers in Bombay, Calcutta and New Delhi were closed, along with the two national wire services, United News of India and the Press Trust of India. Officials of the state-run All-India Radio, which continued to broadcast, said no major paper in the country was publishing.

Indian journalists, editors and publishers also succeeded for the first time in drawing Gandhi into the growing press freedom controversy. The prime minister, who had remained aloof from the controversy over the Bihar press bill and nearly identical measures adopted in two other states, indirectly supported the curbs Wednesday in a sharp attack on "irresponsible" newspapers.

Addressing a Congress-I Party meeting in Lucknow, Gandhi said she had not read the Bihar press bill but understood from government lawyers that it contains nothing to gag the press. She warned that the government could not allow any segment of society, including the press, to misuse constitutional freedom of expression and that just as the constitution does not allow anyone to commit murder, no reporter could be allowed to engage in character assassination.

The Bihar press bill, adopted amid pandemonium in the state legislature on July 31, prohibits the publication, sale and possession of any printed matter that is "scurrilous" or is "grossly indecent" or "intended for blackmail."

Indian newspaper editors say that the bill is so vaguely worded that it can be interpreted as prohibiting any critical reporting on the conduct of public officials.

Even more ominous, according to Satchidanand Sahay, editor of the respected daily, The Statesman, and chairman of the Press Guild of India, is an amendment to the penal code that transfers authority for enforcing the press restrictions from judicial magistrates to executive magistrates, who are political appointees answerable to the state government that drafted the bill.

"That means any journalist the government doesn't like can be locked up without bail for practically anything he writes," Sahay said in an interview. "The whole idea is to terrorize journalists into submission."

While the bill still only applies to Bihar and must be signed by President Zail Singh to become law, Sahay and other Indian journalists said they fear it is Gandhi's first step toward nationwide press censorship.

As the state with the second highest number of members of Parliament, Bihar, which is governed by a Congress-I Party administration, is regarded as crucial to the ruling party headed by Gandhi. To win an election and form a government, it normally is only necessary for a party to control Bihar and Uttar Pradesh, and traditionally those states have been closely monitored by the central government.

While no evidence has surfaced to indicate that Gandhi had a personal hand in advancing the bill, the opposition People's Party leader Atal Bihari Vajpayee has called the Bihar bill "New Delhi's baby" and has said it was written at the behest of the prime minister.

The Bihar press curbs bill grew out of an intense personal feud between Bihar's chief minister, Jagannath Mishra, and Subeshwar Singh, the wealthy owner of the influential local English-language dailies, The Indian Nation and Searchlight.

For months, Mishra, who once had been enthusiastically supported by the local newspapers, was attacked in the press and accused of, among other things, participating in a black magic rite after bathing in goat's blood. One paper charged that Bihar police blinded 31 suspects and detained at least 1,000 others for more than three years, and another reported that admission officials at local colleges took bribes from prospective students.

The blinding stories and disclosures about college admissions bribes were carefully documented, but the free-wheeling Indian press often shows a penchant for a highly personalized style of journalism. Many newspapers, particularly those that oppose Gandhi, routinely weave blatant editorial comment into news columns, and often their sensational "exclusives" remain exclusive for an embarrassingly long time.

Indian journalists recently have come under increasing attacks by the government and by Gandhi, who has said in Parliament that the press is the only opposition she has. The Indian news media, in turn, have been acutely sensitive to the government's attitude because newspapers depend heavily on government advertisements and because the government controls the price and distribution of newsprint.

Nonetheless, the Indian press lately has become aggressive and even strident in its reporting of the Gandhi government. A close adviser to Gandhi and her late son Sanjay, Maharashtra State Chief Minister Abdul R. Antulay, was forced to resign after The Indian Express exposed a kickback scandal involving a state-run cement manufacturer.

Increasingly, reporters and editors complain that they have been arrested, threatened and beaten for antigovernment reporting.