NICOSIA, Cyprus (AP) _ The supreme religious leader of the world's Shiite Muslims was buried today in Iran, amid signs of a power struggle for the succession.

The official Tehran Radio, monitored in Nicosia, referred several times to Iran's spiritual leader, Ayatollah Ali Khamenei, as grand ayatollah, the highest religious rank in the Shiite sect.

That strengthened indications that Iran is intensifying its drive to retain domination of the sect, which has about 100 million adherents around the world.

Any such Iranian move is likely to be challenged by Shiites in Iraq, Iran's historic foe.

The radio said millions of chanting Iranians poured into the holy city of Qom, 80 miles south of Tehran, to attend the funeral of Grand Ayatollah Mohammed Ali Araki. Araki was at least 100 when he died Tuesday.

A live broadcast said the mourners followed a black coffin through the streets to the Hazrat-e Masumeh shrine where Araki was laid to rest.

Although the fundamentalist Tehran government has no official say in the succession, Iran has indicated the next supreme leader must be an Iranian, which is likely to be opposed by Shiites in Iraq and other parts of the world.

There has been no official word that Khamenei, 55, has been promoted to grand ayatollah by Iran's religious establishment.

But the official Islamic Republic News Agency, also monitored in Cyprus, quoted two senior Iranian clerics as saying that he was eligible to ''give guidance in religious matters.''

They referred to him as ''seyyed,'' meaning he claims descent from the Prophet Mohammed, Islam's founder, a clear attempt to demonstrate his religious credentials.

The soft-spoken, enigmatic Khamenei was elected to succeed Ayatollah Ruhollah Khomeini after the revolutionary patriarch who guided the Islamic revolution through its first 10 turbulent years died in 1989.

Shiites, who make up about 10 percent of the world's 1 billion Muslims, are the predominant sect among Iran's 60 million people and the majority in Iraq, Iran's historic foe, and Azerbaijan. Small numbers also exist elsewhere in the Muslim world.