"Human Rights Watch urges the new government of President Mohammad Khatami to implement enforceable legal safeguards available to all and to root out discrimination on the basis of religion or ethnic origin," the New York-based group said.
In a statement, it said the Iranian government had engaged in "the flagrant persecution of religious minorities, notably Baha'is and evangelical Christians."
Analysts say evangelical Christians are pressured by Iranian authorities because of the group's activities in converting Moslem Iranians. Other Christian minorities, such as Armenians and Assyrians, limit their religious activities to their own ethnic groups.
Many senior government and army positions in Iran are limited to Iran's official religion which is Shi'ite Islam.
"Iran's constitution provides only qualified commitments to the principle of non-discrimination on the basis of religion or ethnic identity," Hanny Megally, executive director of Human Rights Watch (HRW) Middle East, said in the statement.
"In practice, these qualified provisions have proved to be no protection against what has become widespread, institutionalised discrimination and, in the case of Baha'is and evangelicals, outright persecution," Megally added.
Iran denies discrimination against ethnic groups and recognized religious minorities -- Christians, Zoroastrians and Jews -- but Tehran does not recognise the Baha'i faith as a religion and considers it "a misleading and wayward sect."
Iran rejects international human rights groups' criticism of its human rights record as politically motivated.
HRW said Baha'i assemblies have been banned since 1983 and participation in Baha'i activities is liable to prosecution.
Baha'is in the United States say more than 200 members of their faith have been executed in Iran for their religious belief since the Islamic revolution in 1979.
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