Iranian authorities raided the headquarters of the major opposition party in the populous province of Azerbaijan today, arrested 11 supporters of one of Ayatollah Ruhollah Khomeini's rivals and four hours later executed them by firing squad.

The harsh and sudden crackdown on a major source of opposition to the central Iranian authority touched off new rioting and bloodshed in Tabriz, the capital of Azerbaijan, and at least four persons were reported killed in the day-long fighting.

In Tehran, meanwhile, Iran's Foreign Ministry said it sent an arrest warrent for deposed Shah Mohammad Reza Pahlavi to Panama, requesting that the exiled monarch be held on charges of mass murder, torture and embezzlement of public funds.

After the arrest, Iranian officials said, Iran would file a formal request with Panama for extradition of the shah.

[In Panama, authorities said there would be no comment on the Iranian request until it had been studied, news services reported.]

Foreign Minister Sadegh Ghotbzadeh denied reports that the warrant was part of a deal in which the United States would accept Iran's right to seek extradition of the ex-shah in return for release of American hostages here.

In Tabriz, the capital of northwest Azerbaijan, dozens of paramilitary forces loyal to Khomeini seized the heavily fortified headquarters of the opposition Moslem People's Republican Party in a predawn attack.

Eleven members of the party, which professes loyalty to the Ayatollah Kazem Shariatmadari, were arrested.

Two of the building's defenders and one pro-Khomeini militiman were killed in the intense fighting at the three-story structure, which has been the site of numerous battles between supporters of the two ayatollahs in recent weeks.

About four hours after the attack, at 8 a.m., the 11 pro-Shariatmadari militiamen had been summarly convicted of fomenting violence and were executed by firing squad at the Tabriz jail.

"They were convicted of killing innocent people," declared Tabriz jail warden Mohammad Ali Yazdani in apparent reference to the 10 deaths and hundreds of injuries resulting from recent clashes in the city.

"They were caught with blood on their hands," he said.

The executions capped a week of anti-Khomeini violence in Tabriz that posed a major threat to the Islamic leader since Shariatmadari's Azerbaijani folllowers make up Iran's largest and wealthiest ethnic minority.

As news of the executions spread across Tabriz this morning, hundreds of Shariatmadari loyalists smashed shops and bazaars and burned banks. There were also reports that a school and an insurance company were set on fire.

Although fighting in Tabriz, Iran's fourth-largest city, has been the most explosive instance of regional discontent in recent days, other provinical uprisings have contributed to distracting Khomeini from the American hostages held at the U.S. Embassy here for 10 weeks.

The Foreign Ministry letter sent to Panamanian officials coincides with the U.N. Security Council debate on economic sanctions against Iran, which was delayed yesterday amid reports of a new Iranian initiative.

Foreign Minister Ghotbzadeh, however, denied in an interview tonight that Iran's U.N. representative was told to offer some alternative approach for satisfying the Iranians and releasing the hostages.

Diplomatic sources here say they believe the Iranians have held fast to their demand for the shah's return, adding that a substantially different approach would require more than the 24-hour delay approved by the Security Council last night.

In the weeks of negotiations since Islamic militants seized the U.S. Embassy, Iranian official have frequently floated new initiatives only to deny them a short time later.

During meetings with U.N. Secretary General Kurt Waldheim here 10 days ago, Ghotbzadeh is believed to have expressed interest in the U.N. envoy's proposal to set up an international panel to vent Iran's grievances against the shah.

But the foreign minister is said to have insisted in his talks with Waldheim that extradition of the deposed monarch remains the critical ingredient in resolving the 10-week crisis with the United States, which Iran holds responsible for the shah's return.

Although the shah received cancer treatment in New York and Texas last month, the left the United States Dec. 15 and is not living with his wife on Contadora Island off the Panamanian coast.

Panamanian President Aristides Royo said two weeks ago he would consider Iran's earlier request to extradite the shah, although the two states have no extradition treaty, but only after the American hostages were released.

Along with the warrant, Ghotbzadeh sent a letter to Royo in which he asked for the arrest of "Mr Mohammad Reza Pahlavi," and said a formal extradition request would follow 60 days after the arrest.

Iranian officials believe they can get around the absence of an extradition treaty with Panama by insisting that the exiled shah is a "common criminal" rather than a deposed ruler seeking political asylum."