Despite a pledge by Ayatollah Ruhollah Khomeini to guarantee their rights, members of Iran's religious minorities are expressing growing concern about their future under an Islamic republic.

Among the most worried are Bahais and Jews -- the former persecuted as heretics for more than a century by Iran's Shiite Moslem majority and the latter caught in the middle of mounting anti-Israel sentiment.

Bahai and Jewish leaders say they trust Khomeini not to renege on his repeated promises to safeguard minorities. They are less confident about some of his more fanatic followers and they fret over Iran's uncertain political and economic future.

So far the Bahais, Jews and other minorities -- notably Armenians, Assyrians and Zoroastrians -- have been largely spared by the Moslem majority during the past year of religious and political upheavals. However, there have been a number of instances in which property belonging to members of religious minorities has been destroyed or damaged.

According to Bahais, two months ago mobs of Shiites went on a rampage in the southern city of Shiraz and burned more than 300 homes belonging to members of the Bahai faith, which originated in the city 135 years ago. In addition, the townspeople took over a Bahai cemetery and divided up the land among themselves. Bahais were also dragged into mosques and forced to denounce their faith.

Similar incidents were reported in the nearby town of Sarvestan and at Miandoab in the northwest.

Businesses and banks in which Bahais were major shareholders also came in for special retribution during the domestic turmoil, which led to the establishment of a provisional Islamic revolutionary government 11 days ago under Ayatollah Khomeini. Two major targets of mob attacks were branches of the Saderat Bank and the Iranian Pepsi-Cola concern, both formerly controlled by Bahai tycoons.

The Bahais, who claim to be the largest non-Moslem minority in Iran, with about 400,000 registered adherents, say four of their members were killed during mob attacks in December. They say presonal property losses come to more than $14 million.

Iran's estimated 100,000 Jews have traditionally enjoyed a more secure status as a religious minority than the Bahais and have avoided the kind of attacks the Bahais have suffered recently. But the Jews have grown increasingly alarmed by the new revolutionary government's hard anti-Israel bent, which appears to them to contain a measure of anti-Semitism.

Khomeini has stressed that his quarrel with Israel stems from that country's role in training the dreaded SAVAK secret police force of the shah.

The new government has cut off oil deliveries to Israel, severed diplomatic relations with the Jewish state and turned the ransacked Israeli mission here over to the Palestine Liberation Organization. A number of Iranian Jews -- further stigmatized by their pro-shah tendencies -- also have been dismissed from public and private sector positions since the Islamic revolution gained the upper hand.

Iran's 300,000 Armenian Christians remember the 1915 massacre of Armenians by neighboring Moslem Turks and many have already left the country. Christians were shocked by the recent desecration of an Americanrun church in north Tehran, although the attack appeared to be mainly motivated by anti-American feelings.

"The biggest problem we face is that we don't know what will happen tomorrow," said a middle-aged Jewish manager of an Iranian construction company. "You can't see any law and order in Iran right now. For us there is a fear of individuals rather than the government. There is no rule in Islam that would threaten Judaism or Jews. What we are afraid of is fanatics in Iran."

He added, "There is a form of anti-Semitism here. It's not against Jews as Jews, but there is a feeling that Jews in Iran are somehow affiliated with Israel."

In fact, many Iranian Jews are pro-Zionist, though now they are keeping such sentiments to themselves.

"The Moslem people here don't like to see that we have a Zionist feeling," a Jewish carpet dealer said.

An estimated 18,000 Jews have left Iran, about 11,000 of them for Israel. However, only 2,000 of those have asked permission to settle permanently in Israel, according to the Jewish Agency there.

Despite their concern, most Iranian Jews intend to stay here, some because they feel attached to this country and others because they have huge business investments.

Iranian Jewish leader Rabbi Yedidya Shufet said, "It's difficult to predict what's going to happen. But I don't think there will be any persecution. We've been living in this country for 27 centuries."

The Bahais generally feel their position is more precarious but they are largely determined to remain in the land where their faith was founded.

They say persecution is nothing new for them: An estimated 20,000 Bahais have been killed in Iran since the eclectic religion was started in 1844 and successive governments have never recognized the faith. The Bahais have never been permitted to build a temple in Iran nor have they been represented in parliament as have other minorities.

The faith is considered heresy because it was founded by the Moslem son of a 19th century minister of the court and it embraces the prophets of other world religions, including Buddha, Jesus Christ and Moses, as well as Mohammed.

The founder and prophet, Baha'ullah, was exiled by the Iranian shah Nasreddin in 1846 and spent the rest of his life in Palestine as a captive of the Ottoman emperor.

Bahais believe in the "unity of mankind" and aim to establish a world government based on Bahai teachings.

"A lot of us are certainly worried about what the future holds in store for us," said a prominent Bahai businessman. "But we've been encouraged by our national assembly not to leave Iran. Our duty is to stay here and serve our country. After all, this is the land of Baha'ullah."