Intelligence agencies of five foreign governments have conducted systematic campaigns inside the United States to spy on, harass and in some cases plan assassinations of their opponents, U.S. intelligence and law enforcement officials have disclosed to Senate investigators.

A principal target of the campaigns by four of the five countries - Iran, the Philippines, Taiwan and Chile - appears to have been American public opinion. Spies were set loose on critics whose speaking out might have disturbed the traditionally close relations between each of the four authoritarian regimes and Washington.

Methods ranged from the reported sending of "hit teams" from Iran and Chile to the United States to the tedious business of monitoring and cataloging student political discussions here by each of the four countries according to a secret Senate staff study of foreign intelligence operations inside the United States. Independent accounts obtained by The Washington Post tend to confirm or expand many of the study's disclosures.

Each service developed its own special wrinkles. Preparing to go totally "underground" when Washington established relations with Peking, Taiwan's National Security Bureau drew up plans to recruit Chinese-Americans to travel to China to spy for Taiwan. Chile hoped to establish a Miami branch office of an international consortium of intelligence agencies it had helped to establish.

But the four spy outfits had an important common feature. All had intelligence liaison agreements with the CIA, and they operated with a relatively free hand here.

The report strongly suggests that SAVAK, the Iranian espionage organization, also had a cozy working relationship with the FBI during 15 years of "significant police, security and nondiplomatic political activity" in the United States by SAVAK.

The Senate study also investigates the cover activities of two communist nations, Yugoslavia and the Soviet Union. Yugoslavia's spy service was the fifth singled out in the study for harasing opponents in the United States Accounts gathered by the FBI and CIA from Croatian and Serbian emigres depict Yugoslav agents posing as diplomats routinely threatening dissidents here with death and then boasting that the U.S. government would not take any action against them.

Unlike the other five spy services, the Soviet Union's KGB is reported by the FBI to concentrate almost exclusively on classical espionage efforts rather than on combatting anti-Soviet views. The one known exception cited by the Senate study involved an unsuccessful Soviet effort to get a Russian Jewish emigre to write anti-Israeli propaganda.

The staff report was based on 45 interviews with intelligence and law enforcement officials completed in January 1979, before the shah's overthrow and also before the Justice Department's indictment of Chilean intelligence officials in the 1976 Washington assassination of former Chilean ambassador to the United States Orlando Letelier and an American citizen, Ronnie Moffit.

The disclosures in the report were labeled "preliminary findings rather than final conclusions." Its purpose was described as being to determine whether more extensive investigation is warranted.

A major conclusion of the study was that none of the agencies most directly involved in the activities of foreign intelligence agents - the CIA, the FBI and State Department - had direct responsibility for monitoring political harassment by foreign governments of their own nationals in the United States.

The Senate report, moreover, has to be impressionistic on points where the FBI, CIA, the State Department, the White House and other agencies have refused to give up sensitive information. It is like most works on intelligency activity in that it has far more details of plans that were never put into effect or did not work than it has of successful operations.

But the report argues persuasively that, even when the foreign intelligence agencies have not carried out their more startling plans, the pattern of "harassment and intimidation" of dissidents had had a "chilling effect" on public discussion and attitudes in this country toward government with controversial human rights records at home.

The intimidation has worked to deprive the targeted emigres, some of whom were naturalized U.S. citizens, of constitutional rights to freedom of speech, assembly and association that are guaranteed to all U.S. residents.

Moreover, the evidence collected strongly suggests that the pattern of intelligence activities may have prevented U.S. officials and citizens from getting accurate information about emigre and student attitudes toward stability and human rights in their home countries.

While President Carter was praising the shah's Iran in January 1978 as "an island of stability," the shah's agents in the United States were intensifying their campaign to silence dissident students who sought to get across a different message, according to intelligence community sources and legal documents filed in Chicago court cases involving the students.

Six months earlier, Taiwan's secret service had organized and paid for an anti-Peking demonstration attended by 1,000 people in Lafayette Square to protest a visit by Secretary of State Cyrus R. Vance to China, the Senate staff report says.

SAVAK, disbanded after the fall of the shah's government in February, and Taiwan's National Security Bureau established the most extensive and active antidissident networks inside the United States of the countries studied.

Iran and Taiwan reportedly set up case officers with diplomatic cover who ran dozens, if not hundreds of agents who infiltrated campus life and student organizations across the country. Each also reportedly planned large-scale propaganda campaigns to be orchestrated through front organizations, according to statements of senior U.S officials quoted in the study.

The most diverse and compelling of the report's six cameo descriptions of foreign spies at work in the United States is the section on Taiwan, which was transformed from being among what one intelligence official calls "the white hats" to the "black hat" camp as Richard M. Nixon and Henry A. Kissinger began their 1971 opening to Peking. The transformation became formal in June 1977, when Taiwan became the only non-communist country to make the FBI's "criteria list."

Countries on the criteria list are monitored by the FBI's counterintelligence division for intelligence activities that "are hostile to, or of particular concern to the national security of the United States." The covert activities of Iran, Chile and the philippines were not regularly monitored by the FBI.

The six countries investigated by the Senate subcommittee staff were chosen because of their "intelligence capabilities, likely motivation and the frequency of alleged wrongdoing." The study's virtual lack of any reporting on the Soviet Union suggests that it may have been included briefly only for ideological balance.