By THE NEW YORK TIMES
 
IO DE JANEIRO, Feb. 17 - The authorities in Paraguay said Thursday that a small left-wing political party with links to guerrillas in Colombia was responsible for the kidnapping and killing of the daughter of a former president whose body was found late on Wednesday in the capital, Asunción.

The victim, Cecilia Cubas, 32, was abducted by several gunmen in a rapid commando-style operation on Sept. 21 as she drove in a suburb of Asunción. The police said Thursday that her body, recovered from the back yard of an abandoned house in a residential area, showed signs of torture. They said that she had been dead about a month.

Senior government officials said Thursday the kidnapping had been organized by a political party called Patria Libre, or Free Fatherland, which works mostly in peasant and worker communities across Paraguay, a landlocked South American nation. The police said that Osmar Martínez, a member of a dissident faction of the group, has been in custody since early this week and that they were looking for other party members and associates.

“They are where they are, disguised as political activists, social leaders or even within the state,” the president of Paraguay, Nicanor Duarte Frutos, said Thursday in an angry speech to the nation of five million people. “We are unmasking a gang of criminals who have been operating under political cover but no longer fool anyone with their habitual lies and cynicism.”

Paraguay’s chief prosecutor, Oscar Latorre, said that Mr. Martínez had been in contact with the Revolutionary Armed Forces of Colombia, a left-wing guerrilla group that has been fighting the Colombian government since the mid-1960’s. He said that investigators had found an e-mail correspondence between Mr. Martínez and Rodrigo Granda, known as the insurgents’ “foreign minister.”

While the Colombian group has carried out thousands of kidnappings in its own country, involvement in an abduction so far from its home base would be highly unusual. In a statement, Mr. Martínez acknowledged meeting Mr. Granda several times, but denied any involvement in the kidnapping of Ms. Cubas.

Her father, Raúl, was elected president in 1998, running as the surrogate of an army general whose own candidacy had been banned after he was arrested and sentenced to prison for insubordination. But Mr. Cubas was forced to step down in March 1999 because of the popular uprising that erupted after the assassination of his vice president, Luis Maria Argana, with whom he had been at odds.

In November, Mr. Cubas, a 60-year-old engineer, said that he had paid a large sum, reportedly $800,000, as a ransom to free his daughter. But the kidnappers said that the payment was merely a “fine,” and then apparently ended communications with the family.

The kidnapping quickly became a national cause célèbre. Marchers took to the streets to protest the crime, bumper stickers calling for the release of Ms. Cubas became popular, banners were posted noting how many days she had been in captivity, and a campaign to legalize the death penalty gained strength.

Some of the protests were directed at the police and the way they were handling the crime. Late last year, for example, neighbors of the house where Ms. Cubas’ body was eventually found alerted the police to unusual activity there, but after a few days of surveillance, the police reportedly abandoned their investigation without searching the house.