CAIRO, JUNE 15 -- Iranian authorities have banned the long-tolerated opposition group of former prime minister Mehdi Bazargan and arrested eight of its members, according to a government statement reported today by Radio Tehran.

The report quoted a statement by the government prosecutor's office in Tehran as saying that Bazargan's Iran Freedom Movement "has acted as a fifth column in the interest of the enemies of the Islamic revolution and the Iranian people," notably during the Iran-Iraq war, which was halted by a cease-fire almost two years ago. The eight arrested include Bazargan's son, Abol Ali Bazargan, and his former commerce minister, Ezzatollah Sahabi, according to news agency reports.

Disclosure of the arrests followed a statement Tuesday by Iran's naval commander, Rear Admiral Ali Shamkhani, that Iran would start patrolling the Persian Gulf with newly acquired submarines and would prevent Iraq from sailing warships through the Strait of Hormuz.

Some analysts said the two events reflect pressure by radicals in the Iranian government against President Ali Akbar Hashemi Rafsanjani, who favors increasing contacts with foreign governments and who responded cautiously but positively to recent Iraqi overtures proposing direct talks for a formal peace treaty.

Bazargan, 84, served as the late Ayatollah Ruhollah Khomeini's first prime minister after Iran's 1979 revolution. He resigned from the post to protest the seizure of the U.S. Embassy in Tehran in November 1979 and since has operated as a token, loyal opposition, not challenging the government's authority, but criticizing it for a lack of political freedoms.

Last month, Bazargan and the eight arrested men were among 90 signatories to an open letter to Rafsanjani demanding greater civil liberties and criticizing the government's handling of the economy. Rafsanjani reacted quickly, saying that "there is no room for deviant currents, dependents of arrogance and politically bankrupt elements."

Some analysts said Rafsanjani's political maneuvering room has shrunk because of his failure to pull Iran out of its economic malaise. "He's facing a very critical, complicated situation," said Egyptian writer Fahmy Howeidi, author of a book on Iran and a recent visitor there.

"He's under pressure from liberals, from the extremists, from the street and from the West. So to face all this pressure he has to be tough."

Shamkhani told the newspaper Ettelaat that if Iraq attempts to sail through the strait, "We naturally have rights, which we will exercise in the no-war-no-peace situation."