The right-wing clerical Islamic Republican Party today appeared headed for outright control of Iran's first revolutionary parliament on the basis of partial early returns.

If that trend is confirmed, the state of the 50 American hostages held since Nov. 4 could be further complicated. Hard-line party members oppose release soon, although that is favored by President Abol Hassan Bani-Sadr. r

They backed the hostages' militant Islamic student captors earlier this week in frustrating a United Nations commission effort to visit the detained Americans.

With 39 provincial voting districts in the 270-seat Majlis, or parliament, decided by the necessary absolute majority, 25 Islamic Republican Party candidates in a field of more than 3,300 had been elected, according to the official Pars News Agency.

If this voting trend continues, the Islamic Republican Party would gain 64 percent of the parliament's seats.

However, the early returns indicated that only about half the constituencies counted had given their candidates a clear majority, forcing run-offs for the remaining seats in about three weeks.

Ayatollah Ruhollah Khomeini, who retains ultimate veto authority over the parliament and may fire the president under Iran's new constitution, said three weeks ago that the parliament would decide the fate of the American hostages.

The early polling results amounted to a kind of revenge for the Islamic Republican Party, which was humiliated in January when Bani-Sadr won the presidential election with 75 percent of the vote.

The results, if confirmed, would raise the specter of a continuing power struggle, pitting a parliament dominated by the Islamic Republican Party and a likely prime minister from that party against the president and his government. Such a situation would strengthen Khomeini's role as the country's final arbiter.

Interior Ministry officials said the parliament could convene immediately if more than two-thirds of the seats are decided as a result of Friday's first round vote.

But specialists said they doubted such an outcome was probate and noted that the runoff vote was scheduled for early April. Final first-round results are not expected before next Thursday at the earliest.

Parliament is not expected to tackle substantive problems until May, although Bani-Sadr has consistently said he would make the hostage issue an early order of business.

As predicted, the turnout was lower than in any previous vote in postrevolutionary Iran. The only effective rule of thumb in explaining various candidates' success was their high recognition factor in a field of relative unknowns.

Among the declared winners today were Sheik Mohammed Ali Montazeri, a young mullah who recently sent a group on Iranians to Syria on an aborted mission to fight Israel; Ayatollah Sadegh Khalkhali, the controversial revolutionary judge who has ordered hundreds of Iranians executed and Rear Adm. Ahmad Madani, a unsuccessful moderate presidential candidate.

Said to be running well in the 30-seat citywide Tehran constituency were former prime minister Mehdi Bazargan and Massoud Rajavi, leader of the leftist Islamic Mujaheddin, a guerrila force that has transformed itself into a full-fledged party.

In Kurdistan, three candidates backed by the still outlawed Kurdistan Democratic Party won first-round election victories.

The Islamic Republican Party, which controlled the state radio and television network for the past month, appeared to owe its gains to its effort to familiarize the public with its leaders.

Bani-Sadr somewhat inexplicably did little to organize an effective party structure and was either unwilling or unable to wrest control of the mass media from his rivals.

In the name of formal fairness, no candidates appeared on radio or television during the campaign proper. Through its majority inside the divided Revolutionary Council, the Islamic Republican Party consolidated its position by pushing through a two-stage election law. The law favors large parties such as the Islamic Republicans at the expense of smaller groups, which had placed their hopes on some form of one-round proportional representation.

Khomeini's election call to Iranians to vote massively against what he considers right- and left-wing candidates also favors the Islamic Republican Party.

So, too, did the confusion in many voters' minds about Bani-Sadr's relationship with the party. Although they are at loggerheads, many Iranians suppose that they are all united in their devotion to Khomeini and his cause.