Persistent charges that government security personnel torture prisoners in Mexico, El Salvador and Guatemala have aroused controversy in those countries in recent months and spawned new efforts to end the practice.

Treatment of prisoners, and respect for human rights generally, appear to have improved somewhat in the past three years in the three nations, particularly in El Salvador. But police and military personnel still apply physical and psychological punishments during interrogation, mostly while trying to extract confessions, according to victims' accounts, human rights monitoring groups, news reports and some government sources.

Torture methods, which vary from country to country, include physical beatings, exposure to extremes of hot and cold, electric shocks and partial asphyxiation by bags over victims' heads, according to these allegations.

The favorite techniques are those that leave few marks. A common Mexican practice reportedly is squirting hot chili powder in carbonated mineral water up the victim's nose.

It is difficult to determine -- and then to curb -- abuses by police and soldiers in the three countries, where the security forces historically have viewed themselves as above the law.

Torture by authorities is practiced in more than 30 countries, according to the human rights group Amnesty International. In this region, acts of torture have been reported most frequently in Guatemala, El Salvador and Mexico, in roughly that order.

There also have been reports of torture in Nicaragua and Honduras, but to a lesser extent than in the other three countries, according to human rights groups. Torture has not been cited as a problem in Costa Rica.

Several dramatic allegations of torture, and new campaigns to eradicate its use, have drawn fresh attention to the issue in this region.

In Mexico, the Sept. 19 earthquake toppled the building that housed the Mexico City prosecutor's office and uncovered bodies of a group of Colombian prisoners that reportedly bore bruises, burns and other marks of torture.

Partly in response to that incident, the Mexican Senate approved new laws in December aimed at stopping torture. That was unusual because the Senate is composed entirely of representatives of the ruling Institutional Revolutionary Party, which seldom takes actions that embarrass the government.

The Senate initiative already has forced the Mexican government to acknowledge publicly for the first time that prisoners are regularly tortured here. Attorney General Sergio Garcia Ramirez said there have been "numerous" cases of torture and abuse of prisoners, although he stressed that police who tortured prisoners acted without authorization.

Most victims of torture here are antigovernment political activists, such as members of peasant unions, according to Amnesty International and Mexican human rights activists. In addition, there are several well-documented cases of torture of persons by police who wanted to extort money from them.

For example, 11 drivers of small vans used as collective taxis in the shantytown of Netzahualcoyotl outside the capital signed a document Oct. 20 charging that police had tortured them while holding them for five days on trumped-up charges and requiring them to pay "fines" of $200 to $2,000.

"On some of us, they put plastic bags over our heads until we felt the anguish and desperation of asphyxiation," the statement said.

Despite the alleged persistence of torture in Mexico, human rights activists said the situation has improved since President Miguel de la Madrid took office in 1982.

"I received more complaints in the previous administration," said Tomas Mojarro, a radio journalist and writer who specializes in gathering reports of torture and other abuses.

In El Salvador, the Roman Catholic Church, Amnesty International and other international human rights groups have charged that continued use of torture by military security forces is a major stain on the human rights record of President Jose Napoleon Duarte's 20-month-old administration.

During interrogations, the security forces regularly keep prisoners naked and blindfolded, deprive them of food and sleep, force them to stand for hours at a time, and threaten to kill the prisoner and relatives, according to victims and to two well-placed sources familiar with treatment of prisoners. There have been less frequent allegations of beatings and use of electric shocks.

"We regret to say that inhumane interrogations and treatment of those captured and accused of political crimes appear to be on the rise," San Salvador Auxiliary Bishop Gregorio Rosa Chavez said in a homily last month. He was referring to an increase in charges of torture during the second half of last year, and he later met with security force officials to discuss his concerns.

Despite the continued reports of torture in El Salvador, however, the problem is significantly less pervasive now than before Duarte came to power, according to victims' accounts and human rights monitoring groups. The security forces, under U.S. pressure, have curbed many of the brutal methods that frequently led to prisoners' deaths at the start of the decade.

Five left-wing guerrillas who were released from prison in October said that prisoners in El Salvador now are tortured only during the first two weeks after their captured. At the end of that period, called "administrative detention," they are transferred to prisons, where they are said virtually never to be abused physically.

"There is no longer torture in Mariona," the nation's main prison for political prisoners, "but torture still is used by the security forces before the comrades reach Mariona," said Salvador Castro Olivares, who was president of the organization of political prisoners in Mariona before his release in the exchange that freed Duarte's kidnaped daughter, Ines, in October.

Guatemala is the country in the region most frequently accused of using torture. The military and police forces allegedly have used torture systematically against real and suspected leftists in a campaign against Marxist rebels.

"The use of torture and ill treatment in an attempt to control all forms of dissent has been a longstanding problem in Guatemala," Amnesty International said in its 1984 report.

Guatemala's new president, Vinicio Cerezo, has tried to curb the abuses by shutting down one of the country's most notorious police units because of accusations that it has tortured and killed suspected leftists in detention.

In another sign of concern over the issue, a new group of Guatemalan political refugees, called the Forum of Guatemalans in Exile, said in a statement here last month, "There cannot be democracy in any country in the world with political assassinations, disappearances and torture."