Record numbers of voters turned out today in what may be the most crucial elections in India's 30 years of independence. The national news agency reported six persons killed and several injured in scattered clashes.

The high turnout raised the hopes of opposition groups, for the election has become something of a referendum on the Congress Party's 30 years in power and the state of emergency declared 20 months ago by Prime Minister Indira Gandhi, who has ruled for the past 11 years.

Result of the elections, in which some 320 million voters are eligible to cast ballots for 542 seats in Parliament, will not be known until Sunday night.

This is India's sixth general election since independence and the first in which a single, united opposition group in challenging the Congress Party.

It is also the first time that the country's 85 million socially shunned but politically powerful "Untouchable" are expected to vote against the ruling party.

The acknowledged leader of the caste, Jagjivan Ram, broke with the prime minister last month, resigning from the Cabinet and the party.

Adding to the impact of Ram's defection is the Untouchables' resentment to the government's aggressive sterlilization program, part of a national bid to keep the country's population of 620 million from growing by 13 million people a year.

There have been reports of Indians - generally poor and from the lowest castes - being sterilized forcibly or undergoing repeated vasectomies.

More frequent are cases in which they reluctantly undergo sterilization to qualify for subsidized housing, free medical care or some form of license, which many states have made contingent on birth-control surgery.

Ironically, as the Untouchables have deserted the Congress Party for the opposition, several of the nation's former princes - stripped of titles and government incomes in 1971 - have either withdrawn from the election or gone over the ruling party.

Many of them retain considerable political and popular influence in their home areas, but some say that their opposition to the Congress Party has proved to be too costly - especially since Gandhi detained several opposition princes and princesses under her emergency regulations. They have all been freed since.

In the last election, 31 former princes ran as candidates and 16 of them won seats in Parliament.

Meanwhile, the opposition - centered around the people's Party, formed of four important non-Communist parties - has been working hard to reinforce the Hindu-Moslem solidarity that was a factor in winning independence from Britain 30 years ago.

At a gathering at the beginning of the month, Moslem dignitaries and politicians shared a platform with Hindu priests and leaders of the Hindu party for the first time since independence.

A huge crowd chanted the old independence slogan "Hindu-Moslem-Sikh-Christian" enthusiastically, and some observes said that the forced resettlement program in Old Delhi and the sterilization effort had cost the Congress Party the nearly automatic loyalty it had enjoyed among the capital's Moslems.

Others have noted a growing defensiveness in the tone of campaign speeches by Prime Minister Gandhi, her politician son Sanjay and other Congress Party candidates.

Today's heavy turnout was seen as a further sign of anti-Gandhi and anti-Congress Party sentiment. Reports from around the country indicated that more than 60 per cent of those eligible had voted in the 300 constituencies involved in the first round of balloting, and in Bombay 85 per cent of the voters were reported to have cast ballots.

In previous elections, heavy voting has always favored the Congress Party's opponents; the previous record turnout, 61.3 per cent in 1967, was also the party's most serious loss to date.

Today, People's Party officials were saying that the turnout had surpassed all expectations.