BERLIN -- On a chilly September night last year, two masked gunmen burst into the back room of the Mykonos restaurant here and, in a bloody scene repeated again and again during the last decade, opened fire on expatriate opponents of Iran's fundamentalist Islamic regime.

This time the targets were a Kurdish separatist leader and three of his top aides. As in dozens of similar murders, investigators found few clues except for four bullet-riddled bodies sprawled amid the overturned tables and shattered cups.

Yet, unlike nearly all of the previous assassinations in France, Switzerland, Italy, Turkey, and at least eight other countries, this time alleged killers soon were caught. Five defendants, including an Iranian accused of being an agent of Tehran's Ministry of Intelligence and Security, known in Persian as VEVAK, are now on trial in Berlin.

Extraordinary security measures include defendants' docks encased in bulletproof glass, double searches of all lawyers and spectators, and an anti-grenade net draped at the court entrance.

The Mykonos murders have refocused public attention in Europe on the systematic extermination of Iran's political foes, as well as the West's relations with Tehran. The investigation and trial have provided new insights into the operation of meticulously organized death squads directly linked to the rule of Iranian President Ali Akbar Hashemi Rafsanjani, according to U.S. and German officials.

The bold brutality of such killings has triggered protests from human rights groups and Western governments. Amnesty International issued a report last week documenting and condemning the murder of Iranian dissidents abroad. "We're seeing a growing pattern of killings and this bloody trail leads back to Tehran," James O'Dea, Washington director of the organization, said in an interview.

Sweden ordered the expulsion of three Iranian diplomats on Monday for spying on Iranian expatriates; Tehran retaliated on Wednesday by kicking out three Swedish diplomats. The State Department has declared Iran to be the most active of all state sponsors of terrorism. It alleges that Iranian agents or surrogate groups carried out more than 20 attacks in 1992 alone.

Leery of Provoking Iran

Despite such recent measures, the West's response to Tehran's alleged complicity has often been tepid or inconsistent. Commercial interests and desires to avoid provoking Iran sometimes have caused Western governments to soft-pedal their criticisms, U.S. and European officials say.

Germany's Federal Criminal Office noted that although "Iran does not shrink from committing serious crimes in pursuing its opponents," the "reaction in the West is most likely to be verbal."

Germany, which sold more than $5 billion in goods and services to Iran last year, is a case in point. In early October, three weeks before the Mykonos trial opened, Chancellor Helmut Kohl's top intelligence adviser, Bernd Schmidbauer, met in Bonn with Ali Fallahian, Iran's intelligence minister. Fallahian, whom the German press has dubbed "the sixth defendant" in the Mykonos murders, is suspected by prosecutors of being the mastermind of the attack.

But when investigators suggested filing charges against Fallahian during his visit, Bonn insisted that the Iranian was a "state guest" who was not to be harassed, according to state prosecutor Bruno Jobst.

Schmidbauer has defended his talks with Fallahian by suggesting that Germany is trying to mediate between Tehran and Western countries that prefer to isolate Iran as an international outlaw. "If you don't cooperate internationally," he told the German newspaper Die Welt, "you get crimes on your own soil."

The Iranian government has denied any connection to attacks. A spokesman for the embassy in Bonn reiterated those denials, adding that allegations of complicity in the Mykonos case "are absolutely baseless. . . . We also want to find out who's behind the murder."

German law enforcement officials say, however, that the six judges presiding over the Mykonos trial will find ample evidence of Iranian government involvement. They note that on Aug. 30, 1992, Fallahian told an Iranian television interviewer, "We track them {opposition groups} outside the country, too. We have them under surveillance. . . . Last year, we succeeded in striking fundamental blows to their top members."

Iranian in the Dock

Less than three weeks later, another blow was struck with the four Mykonos murders. Of the five men arrested -- one questioned shortly after the shootings confessed and implicated the others -- four are Lebanese with links to Hezbollah, the pro-Iranian extremist group. The fifth man is Kazem Darabi, 34, an Iranian vegetable vendor who moved to Germany 13 years ago and has been convicted previously of attacking Iranian dissidents.

The indictment charges that Darabi "was an agent of the Iranian secret service VEVAK and a member of the Iranian Revolutionary Guard with close ties to Hezbollah in Lebanon." The indictment contends that Darabi "received from VEVAK the secret service's order to liquidate" the leader of the Kurdistan Democratic Party of Iran (PDKI) while he was in Berlin for a conference.

Although not in the Mykonos restaurant when the killings occurred on Sept. 17, 1992, Darabi allegedly recruited the assassins, organized the plot, provided the weapons and orchestrated the escape. The Berlin attack "is the consequence of countermeasures against the Iranian opposition, particularly the PDKI, as personally described by the secret service minister" Fallahian, the German Federal Office for the Protection of the Constitution asserted in a report that formed the basis of the indictment.

The Berlin murders are only a recent example of what intelligence and law enforcement officials say is a campaign that has not diminished since the death of Ayatollah Ruhollah Khomeini in 1989 and Rafsanjani's accession. "Behind all these crimes stands a sovereign state with all of its logistical capabilities," the German Federal Criminal Office report asserted.

An Iranian resistance movement, the People's Mojahedin, contends the Tehran regime has killed 100,000 opponents in Iran and tortured another 150,000. The organization, which is unrelated to the anti-communist Afghan guerrillas called mujaheddin, lists nearly 100 assassinations of or assaults on Iranian expatriates since the fundamentalist regime took power in 1979. Western law enforcement officials have found links to Tehran in many of these cases. Among them:

On March 16, Mohammed Hussein Naghdi, a leading dissident with the National Council of Resistance of Iran, was shot in the face and killed while sitting in his car in downtown Rome. The two assassins escaped on a motorcycle through midday traffic. The Italian interior minister subsequently described the murder as "part of an extremely dangerous strategy {by Islamic fundamentalists} aimed at subverting Europe and the West."

In Turkey, approximately 50 Iranian dissidents have been killed, as well as secular Turks who spoke out against Iranian fundamentalism. Among the attacks was the kidnapping in Istanbul on June 4, 1992, of Mansour Amini, a member of the People's Mojahedin. His body, with its fingernails pulled out and genitals mutilated, was found in a shallow grave. Nineteen Turkish fundamentalists eventually charged with Amini's murder and two other killings had "clear connections to Iran," according to Turkey's interior minister.

Abdul Rahman Qassemlou, leader of the Kurdistan Democratic Party of Iran, and two associates were shot to death in Vienna in 1989, after being lured to a meeting with representatives from the Tehran government. An arrest warrant was issued for two Iranian gunmen and the Austrian foreign minister said it was "probable" that Iran was behind the killings. Qassemlou's successor, Sadeq Sharafkandi, was the primary target in the Berlin killings three years later.

Former prime minister Shapour Bakhtiar, 76, had his throat slit and his secretary was stabbed to death outside Paris on Aug. 6, 1991. An investigating French magistrate uncovered an extensive terror network that helped the assassins carry out the murder and escape from France using forged passports. Several arrests have been made in the case and warrants issued for two Iranians. U.S. intelligence officials have termed it unlikely that such a high-level assassination would have been undertaken without Rafsanjani's approval.

Another Iranian dissident and close associate of Bakhtiar, Abdel Rahman Boroumand, was stabbed to death in Paris in April 1991. The former prime minister had eluded an earlier attempt on his life in 1980, when men posing as journalists killed a French policeman and a neighbor in a shootout at Bakhtiar's house. The convicted leader, a pro-Iranian Lebanese, was released in 1990 in a swap for French hostages in Lebanon.

The Norwegian publisher of Salman Rushdie's "The Satanic Verses" was wounded by three bullets outside his Oslo home in mid-October. Rushdie, a British author accused of blasphemy by Khomeini, has been in hiding since 1989, when Tehran issued a death warrant and put a $2 million bounty on his head. The Japanese translator of "The Satanic Verses" was murdered and an Italian translator escaped an assassination attempt in 1991.

Other Iranian dissidents killed in recent years include Bahman Javadi, shot by a gunman using a silencer-equipped pistol on Cyprus in 1989; Ataellah Bayahmadi, a former colonel in intelligence, shot in his hotel room in Dubai in June 1989; and Majid-Reza Ibrahimi, a Mojahedin member shot while shopping in Baghdad last month.

Swiss Collect Evidence

Perhaps the case that offers the clearest link to Tehran was the murder in Switzerland on Aug. 24, 1990, of Kazem Rajavi, head of the Mojahedin organization in Geneva. While driving home from a tobacco shop, Rajavi was ambushed by gunmen in two cars. After pinning Rajavi's red Datsun against the curb, one assassin opened fire with an Uzi 9mm submachine gun. Six bullets hit Rajavi.

Swiss police and magistrate Roland Chatelain subsequently implicated 13 Iranians in the plot. Most had entered Switzerland with diplomatic passports issued in Tehran on the same date with the notation "on assignment." Most also had arrived on Iran Air's Tehran-to-Geneva flights over several months preceding the murder, using tickets with consecutive serial numbers, according to Chatelain's report. Several of the men flew from Geneva to Vienna less than two hours after the killing.

The accumulated evidence, Chatelain declared, "permits confirmation of a direct involvement by one or more official Iranian services."

Some observers charge that the West's efforts to counter the murder spree ring hollow. "Given the seriousness of a government sending its agents out to kill opposition leaders, the response has been inadequate," said O'Dea, Amnesty's Washington director. "There is routine torture, routine levels of repression. And because the pattern is repeated, governments have accepted that it is now the norm for Iran."