BUENOS AIRES, Argentina (AP) _ Former President Juan Peron's hands were severed and stolen by thieves who broke into his tomb, a judge confirmed Thursday, and authorities investigated possible links between the thieves and ultra-rightists.

Civil Court Judge Jaime Far Suau said the thieves also took Peron's sword and a letter from his third wife during a break-in last weekend at the Peron underground vault at Chacarita Cemetery, just days before Wednesday's 13th anniversary of his death.

The judge ordered the coffin opened for examination after the presumed thieves asked for $8 million ransom.

The Argentine flag that draped his coffin and Peron's uniform cap, at first believed stolen, were found inside the wooden casket, the judge said.

President Raul Alfonsin described the mutilation of Peron's corpse as ''a macabre act,'' and said those responsible ''conspire against the peace of Argentina and insult the memory of Gen. Peron.''

Similar events have happened twice before in recent Argentine history, beginning with the 1955 theft of the body of Peron's second wife, Eva Peron, and the 1974 stealing of the corpse of former President Pedro Aramburu.

Peron, the most popular Argentine leader of the 20th century, was president three times from 1946 until his death July 1, 1974. He was succeeded by Isabel Peron, his third wife and then-vice president.

Paying ransom is not under consideration, said Sen. Vicente Saadi, a Peronist Party leader.

''This profanity has doubtless political motives destined to introduce fear and commotion in society and to maintain that feeling right up to the (Sept. 6 gubernatorial and municipal) elections,'' said Minister of the Interior Antonio Troccoli.

Authorities were looking into possible links between the thieves and ultra- rightists believed responsible for 16 bombings last week at offices of Alfonsin's center-left Radical Civic Union Party.

Other politicians discounted that theory.

''This all is simply an episode which is macabre, an act by a group of psychopaths,'' said House of Deputies leader Antonio Cafiero, Peronist candidate for governor of Buenos Aires province, the most populous in Argentina.

''For the good of everyone's conscience, the government should quickly clear up this episode,'' said Saul Ubaldini, head of the powerful 4-million- memb er General Confederation of Labor.

Ubaldini's group is the backbone of support for the Peronist Party, chief rival to Alfonsin's party.

The body of Eva Peron, who died in 1952, was secreted out of the country in 1955 by Aramburu's men for reburial in a secret tomb in Milan, Italy, where it remained for nearly two decades.

Aramburu, president of the military regime that replaced Peron in a 1955 coup, was assassinated in 1970 by a leftist faction of the Peronist Party called the Montoneros for crimes against Peronists during his rule and for concealing the remains of Evita, as she was popularly called.

In 1974, Aramburu's remains were stolen and remained missing for about a month until a deal was struck in which the government announced the ''miraculous'' discovery of the body of Evita, which would be returned from Europe.

The country was captivated by the 1974 journey of Evita's remains, in Peron's possession, from Milan to Madrid, Spain, and then on to Buenos Aires, where they were placed in an elaborate tomb at Recoleta Cemetery.