A right-wing coalition dominated by the clerical Islamic Republican Party today emerged as the most organized force in the first round of Iran's complicated parliamentary elections.

In Tehran, where 433 candidates competed for 30 seats in a single city-wide constituency, specialists interpreted today's turnout as suggesting that the clerical hard-liners may have scored a substantial victory at the expense of President Abol Hassan Bani-Sadr.

No official results were announced today nor are they expected before next Thursday at the earliest. But random surveys and other indicators here pointed to a very successful election drive by the religious leaders.

If this pattern in Tehran were repeated throughout the country, the new 270-seat parliament would have a majority opposed to early release of the estimated 50 American hostages Embassy since Nov. 4.

The clerical hard-liners have backed the militants to the hilt. Together they succeeded in humiliating Bani-Sadr, who long has favored early resolution of the hostage question, by frustrating the United Nations commission in its recent efforts to visit the detained Americans.

Iran's spiritual leader, Ayatollah Ruhollah Khomeini, has said the hostage question will be decided by the new parliament. But with the final runoff election scheduled for early April and the chamber scheduled to meet April 21, a leading Revolutionary Council member today said the deputies were unlikely to tackle serious business for yet an additional month.

The first-round results next week will winnow the front-runners from among the 3,500 candidates unable to win the required absolute majority.

The voting today was marred by leftist charges of fraud -- principally involving Islamic militants who filled out voting forms outside the polling stations for the illiterates. As much as half the adult population is believed illiterate.

Helping the Islamic party was its past control of the government-run radio and television monopoly, which familiarized Iranians with their leaders over the months. No radio or television coverage of the election campaign was allowed, thus considerably hurting candidates backed by Bani-Sadr or small left- or right-wing parties.

However, many Iranians proved eclectic voters, picking out, say, a mullah, a moderate such as former prime minister Mehdi Bazargan and Massoud Rajavi, the leader of the left-wing Mujahideen. The only obvious common denominator in such cases was that all these men were easily recognized by a public confronted with hundreds of largely unknown candidates.

Also damaging to the small parties was the electoral law imposed by the religious leaders that set up a French-style, two-stage election basically favoring large, well-organized groups such as their own.

Khomeini may have indirectly contributed to the Islamic party's success by asking Iranians to renew their confidence in the president and the Revolutionary Council.

Although the Revolutionary Council's deep divisions are well known abroad and among educated Iranians here, many Iranians are not aware of the power struggle within its ranks, and Khomeini's message was taken as an endorsement of candidates favored by council members.

Bani-Sadr's campaign never got off the ground in Tehran, and his backers have placed their hopes in cities such as Shiraz and Isfahan and other provincial centers.

Many Iranians in the middle-class bastions of north Tehran abstained, apparently dispairing of electing lay candidates who shared their anticlerical viewpoint. Many educated Tehran residents favored extreme leftist candidates of the pro-Moscow Communist Party, the Mjuahideen or the Marxist-Leninist Fedayeen.

The citywide constituency devised for Tehran favored the religious leaders, since it minimized the impact of neighborhood voting.

The Interior Ministry today extended the election ban in Kurdistan from the major city of Sanandaj to the smaller towns of Baneh, Mariban and Saqqez, claiming free elections were impossible because of the presence of armed groups.

The turnout today was difficult to gauge. But fewer Iranians have taken part in every successive vote since they were asked to abolish the monarchy and endorse the Islamic republic in March 1979.