Amnesty International says 1 nation in 3 treated prisoners cruelly

* In Haiti, government torture and ill treatment of prisoners are a regular occurrence. Although vociferous international protests have occasionally forced the release of internees, not a single complaint of human rights abuse has been investigated by the Port-au-Prince authorities.

* In Iran, the practice of executing and brutally maltreating political detainees continues in much the same way as in the years of the Shah's rule. The present Islamic revolutionary leadership has ignored all requests by human rights organizations to verify violations, arguing that the allegations of released prisoners and relatives are ''totally imaginary'' and the ''fruits of antirevolutionary propaganda.''

* In Afghanistan, since the Soviet invasion, detailed testimony and other reports indicate that political suspects held by the Soviet and East German-trained Khad (state information police) have been subjected to beatings, deprivation of sleep, electric shocks, and other forms of torture, sometimes resulting in death. Apart from controlled visits to Pul-e-Charkhi prison in Kabul by the International Committee of the Red Cross in 1980 and 1982, no humanitarian organization has been allowed to visit this or other notorious detention centers.

According to a report just published by Amnesty International (AI) in London, 1 out of 3 countries has tortured or cruelly treated prisoners since the beginning of this decade. The Amnesty report was issued to mark the start of a new campaign to expose and end the use of torture as a ''tool of state policy.''

In its 263-page report titled ''Torture in the Eighties,'' the human rights organization makes charges of physical and psychological abuse in 98 nations. It acknowledges that state cover-ups, intimidation of witnesses, and censorship often make corroboration of claims difficult, but says the evidence that does exist demonstrates that some governments have made a conscious decision to torture and that other governments have shown a lack of will to stop torture. The report also is careful to say that it does not intend its report to be a world ''blacklist.''

Since the 1970s, the report notes, many governments practicing torture have changed. Some of these have ceased ill-treatment of prisoners. Others, such as Iran and Zimbabwe, have not prevented the recurrence of torture, the report says. AI further maintains that while no torture experience is typical, a discernible pattern has emerged from the thousands of personal testimonies and statements that have reached Amnesty in London.

For the individual victim, the report says, torture can mean being seized at night, violently, while family members and neighbors are helpless. It can mean being blindfolded and beaten in a police van or unmarked car, or being held in isolation for days, weeks, or months on end. Torture can also mean ''the pistol cocked at the temple,'' the meticulous procedure of mock execution by firing squad, or burial alive in a deserted area.

''Each is a means of demonstrating to the victim that the team of torturers has absolute power,'' the report said.

Although torture remains a major international problem, claims AI, increased efforts ranging from United Nations' condemnations to journalistic investigations have helped to make the public more aware of what can be done to help from abroad.

AI has intervened on behalf of more than 2,500 individuals exposed to torture in 45 countries since January 1980. It calls for speedy response by cables and express letters from around the world on behalf of a person known by name who is at risk of being ill treated.

AI, which launched its first campaign for the abolition of torture in 1972, maintains that for this type of action to be effective, the organization must receive reliable details quickly. Torture, Amnesty emphasizes, usually occurs in the first few days or weeks of detention. But information about such activity can lead to exposure, ''a key to stopping an individual's suffering and to pressing a government to abandon the practice.''

AI is urging the adoption of an international anti-torture convention now being drafted by the UN. It says that more than 30,000 volunteers in 47 countries have already joined a special standby system to send urgent appeals in cases where torture is feared. ''Revulsion at the extermination camps of the Second World War led to a convention outlawing genocide for all time as a crime against humanity,'' the report says. ''Today's torture chambers demand a similar international response.''