BUENOS AIRES -- A prominent financier disappears in Argentina. More than $1 million is paid as ransom but he is not returned. Although police investigators implicate several Army intelligence agents in the crime, the case remains open more than two years later.

For the administration of President Raul Alfonsin, the failure to solve the July 1985 abduction of banker and real estate investor Osvaldo Sivak stands out as the embarrassing and troubling symbol of the government's impotence against extreme right-wing squads that still haunt Argentina.

These rogue bands, described by government officials as vestiges of military rule and composed of former and current agents of the military intelligence and police services, continue to kidnap, bomb, steal and threaten. Within the past two months, they have been accused of robbing the tomb of Juan Peron and bombing more than a score of political party headquarters and houses of judges and military men loyal to the government.

Their aim, officials say, is to promote a climate of fear and instability in order to make Argentine democracy, now 3 1/2 years old, look too weak to protect the public.

While the attacks have struck at just a small sector of society, and few have left casualties, the violence has unnerved a country psychologically scarred by the terrorism of the 1970s. Surveys show that while most Argentines perceive little personal danger, a collective sense of insecurity lingers.

Similar anxieties, though much more acute, prompted the armed forces to overthrow constitutional authorities in 1976. Military commanders then conducted a campaign of kidnaping, torture and murder aimed at eliminating not just the insurgents but most dissent.

Britain's defeat of Argentina in the Falklands War so discredited military leaders that they withdrew from power in 1983. But Alfonsin and his aides have been unable to rout all antidemocratic forces from sensitive state jobs, particularly in the military intelligence services.

The roots of these units run deep. Paramilitary groups were employed not only by the military regimes but also, earlier, by the constitutional government of Isabel Peron.

"There is nothing more difficult than penetrating the intelligence services," Alfonsin said last year.

Interior Minister Antonio Troccoli complained last month about "enemies from within" and called the security issue "the most vulnerable aspect of the transition" from military dictatorship to democracy.

Circumstantial evidence points to the ultra-right as the source of the problem. In June, for instance, bombs exploded at 16 provincial offices of the governing center-left Civic Radical Union. According to newspaper accounts, the bombs had been fashioned from a plastic explosive imported by the armed forces and fuses and timers manufactured by military-owned enterprises here. So far, no arrests have been reported.

In July, thieves broke into Juan Peron's monumental tomb and severed the hands of the embalmed former president. Investigators have linked the tactics and evident political purpose to the right-wing crime campaign.

Government officials say left-wing groups, politically active again in Argentina on a minor scale, lack the organization and funds for such attacks. "The far left opposes the government but is not involved in destabilization," said Facundo Suarez, the chief of state intelligence, in a recent magazine interview.

The capture of some groups this year has reinforced the notion of an ultra-right plot.

A paramilitary band found operating out of the Buenos Aires suburb of Moron is being held responsible for a commando raid against a radio station transmitter, an explosion at a Communist Party office and a bomb planted at the house of a federal judge. The group reportedly also distributed leaflets calling on police to form death squads to "annihilate" corrupt judges and politicians.

Currently under detention on suspicion of leading the cell is Patricio Camps, son of Army ex-general Ramon Camps, the former head of the Buenos Aires provincial police who is now imprisoned after conviction in scores of torture cases.

Police say a second terrorist unit was broken up in the southern city of Comodoro Rivadavia with the arrest of an Army officer and three military intelligence agents. The police have tied the group to bombings of leftist party offices and the house of a local forensic physician.

Among the arms, ammunition, military uniforms and falsified identification papers confiscated was an Air Force missile.

Trying desperately to separate friend from foe in government ranks, the Alfonsin team has at times shown its inexperience and, once last year, stumbled into scandal. In the Sivak kidnaping case, after an initial $1.1 million ransom payment failed to free the financier, Minister Troccoli was revealed to have passed $25,000 -- and encouraged the victim's family to pay $275,000 -- to a three-man military intelligence unit thought to be in contact with the kidnapers.

The three agents, along with a female accomplice, never produced Sivak and subsequently were arrested for extortion. News of the back-channel effort caused a political uproar and triggered the resignations of the minister of defense and the Buenos Aires federal police chief.

Hampering Alfonsin's attempts to expose and destroy the terrorist network has been his inability to establish firm control over the armed forces, which resent the government's condemnation of their 1970s "dirty war."

At the National Intelligence Center, which coordinates state intelligence gathering, civilians have taken full charge and have ousted all military personnel. But in the absence of a strong chain of military command, Alfonsin has sought simply to reduce the activity of the military intelligence services, especially the Army's notorious Battalion 601.

Restraining Alfonsin from moving too forcefully against suspected plotters in the spy agencies, some speculate, may be the fear of provoking further attacks or opening a Pandora's box of state secrets.

"The power of the intelligence services here is such that one can never be certain whether they are dominating the government," said Jorge Sivak, a brother of the abducted financier. "Could it be that Alfonsin has made a deal with them? Does he hope to avoid further disruptions in this sensitive political transition period? Is he worried about spilling secrets? I don't know, but some political will is missing to go after the culprits."