Iran's unofficial head of state, Ayatollah Ruhollah Khomeini, today turned down a Kurdish peace bid and refused to endorse a negotiated cease-fire as Islamic firing squads executed 20 persons accused of involvement in last week's Kurdish revolt.

A senior aide to Khomeini said the ayatollah "made no concessions" to the Kurds on their proposals for an end to fighting between rebels and government forces in the turbulent Kurdistan Province of western Iran.

Abolhassan Bani-Sadr, in remarks that he said reflected Khomeini's views, said, "There is no justification whatsoever for the systematic subversion of minorities which want to impose violence on our people. As soon as they stop acting in this manner, brotherly Islamic cooperation can begin.

"It is not up to us to declare a cease-fire," he said.

According to the state radio, Khomeini said of the Kurdish offer to talk: "The purpose is not that you negotiate with the criminal leaders. They must be crushed."

Nevertheless, in apparent disregard of Khomeini's hard line, an official cease-fire remained in force on all fronts in the Kurdish region for the second day as both sides awaited the outcome of peace moves in Tehran.

The spokesman for a five-man Kurdish delegation said last night that Ayatollah Mahmoud Taleghani, the government's main troubleshooter on minority issues, had given assurances that a formal cease-fire would be announced today. But Khomeini's attitude has apparently scuttled those plans.

In the Kurdish stronghold of Mahabad, meanwhile, a spokesman for the Kurdistan Democratic Party said peace moves were being threatened by the continued execution of Kurds alleged to have participated in the fighting against government forces.

The official Pars news agency reported that 20 more persons were executed in the Kurdish town of Saqqez today on the orders of Iran's chief Islamic revolutionary judge, Ayatollah Sadegh Khalkhali. Saqqez was overrun Sunday by government forces after five days of heavy fighting with Kurdish rebels.

Nine of those executed were soldiers, the first to be shot for offenses committed since the February revolution. They were said to have deserted the army and aided the rebels in the Saqqez fighting last week.

The Kurdish spokesman in Mahabad said thousands of townspeople today demanded that Islamic Revolutionary Guards in custody at the city's military garrison be killed in retaliation for the Saqqez executions.

Ayatollah Khalkhali has ordered the execution of at least 77 persons, nearly all of them alleged Kurdish rebels, since he was dispatched to Kurdistan two weeks ago by Khomeini. His recall from the Kurdish region was one of the main demands presented to Iranian authorities in Tehran yesterday by Kurdish negotiators.

Other demands in a three-point Kurdish peace plan were an immediate cease-fire declaration and the convening of a conference "to solve the Kurdish problem through peaceful means."

In other developments:

Turkish Interior Minister Hasan Fehmi Gunes, touring Kurdish areas of eastern Turkey near the Iranian boarder to investigate reports of separatist activity, said there was no threat to the integrity of the Turkish state in the area.

The Iranian Foreign Ministry said a Soviet delegation will visit Tehran to liquidate the assets of the Soviet-owned Russo-Iran bank following Iran's bank nationalization in June.