Iranian Foreign Minister Sadegh Ghotbzadeh, who has avoided the limelight of Iranian politics since last month's rumors that he was about to be dismissed, reappeared yesterday to deliver a strong attack on the Soviet Union, denouncing it as "no less Satanic" than the United States.

At the same time, Iran's new prime minister, Mohammad Ali Rajai, consulted with various groups of hard-liners on the selection of a Cabinet that almost certainly will drop Ghotbzadeh and other moderates from the government.

Ghotbzadeh's remarks, accusing the Soviet Union of interfeariang in Iranian affairs and demanding it get out of neighboring Afghanistan, were contained in a letter addressed to Soviet Foreign Minister Andrei Gromyko.

The letter, delivered to the Soviet Embassy in Tehran and broadcast over Tehran radio, contained a compendium of Iranian complaints against the Kremlin and was written in reply to a note from Gromyko.

"Our imam [Ayatollah Ruhollah Khomeini] has described the U.S.A. as a big Satan. Unfortunately, you too have proved in practice that you are no less Satanic than the U.S.A.," Ghotbzadeh told Gromyko.

Ghotbzadeh accused the Kremlin of giving arms to Kurdish rebels fighting for autonomy, supporting the pro-Moscow Tudeh Party and using its embassy and consulates to spy on Iran.

In another development, nine Western diplomatic heads of mission called on the speaker of the Iranian parliament to urge the release of the American hostages, diplomatic sources said yesterday.

But the sources said the only concrete result of the meeting Wednesday was that the speaker, Hojatoleslam Ali Akbar Hashemi Rafsanjani, agreed to pass on the views of the envoys to the parliament.