Carlos," the world's most wanted and elusive terrorist, has resurfaced for the first time in six years with a letter threatening unspecified action against the French government and its interior minister unless two radicals are released from French jails within a month.

Interior Ministry officials said the half-page letter in Spanish was sent to the French Embassy in The Hague, marked for authenticity with two thumb prints that authorities verified as those of the 32-year-old, Venezuelan-born terrorist whose real name is Ilich Ramirez Sanchez.

Carlos, believed to have been the leader of the raid that kidnaped 11 oil ministers from a meeting of the Organization of Petroleum Exporting Countries in Vienna in 1975, threatened Interior Minister Gaston Defferre by name.

Agence France-Presse said the following was the "substance" of the letter: "You have arrested two members of my organization although they had no special orders to carry out an attack on French territory. I give you a month to release them. Otherwise I will personally attack the French government and more especially Interior Minister Gaston Defferre."

Jean Jurgensen, French ambassador to the Netherlands, has been provided with a bulletproof limousine and increased police protection since the letter was received, officials said.

The letter, which the newspaper France-Soir said was delivered March 1, marked the first time that Carlos had done anything so self-identifying since the 1975 attack in Vienna, which left three people dead and eight wounded in the name of a "total liberation war" against Israel.

After four days of negotiations, Carlos, his team and their hostages were flown to Algiers, where the ministers were released and the terrorists vanished.

In the meantime, his reputation has been kept alive less by his actions than by two best-selling novels depicting Carlos or a character based on him: Frederick Forsythe's "The Day of the Jackal" and "The Fifth Horseman " by Larry Collins and Dominique Lapierre.

The two prisoners whose freedom Carlos has demanded are Bruno Breguet, a 34-year-old Swiss, and West German Magdalena Kaupp, 34.

French police arrested them Feb. 16 after a chase that began in an underground parking lot on the Champs-Elysees when watchmen challenged the pair as robbery suspects.

Breguet, condemned in Israel in 1970 to a 15-year sentence for possession of explosives but released seven years later, twice tried to fire a 9-mm Herstall automatic pistol at pursuing French police, but his weapon misfired.

The couple were charged with attempted homocide, death threats, falsified idenity papers and illegal possession of the pistol, 4.4 pounds of explosives and two small bottles of cooking gas. Their Peugeot 504 car had phony license plates and they were carrying $2,000 in cash, police said.

Agence France-Presse said that Kaupp was under West German police suspicion of belonging to a terrorist group and quoted an unidentified French court source as linking her with Johannes Weinrich, an alleged member of the Baader-Meinhoff terrorist gang in West Germany.

The Interior Ministry spokesman said that the letter demanded that Breguet and Kaupp be "flown to a destination of their choice."

Carlos' first known attack was on Dec. 30, 1973, when he claimed responsibility for shooting Joseph Conrad Sieff, a wealthy British Jew, three times in the face in London. Sieff survived.

On Sept. 3, 1974, he attacked the French Embassy in The Hague and forced France to release from jail Yutaka Furuya, a Japanese Red Army terrorist, in exchange for hostages.

Carlos claimed responsibility for the grenade attack two days later on the Jewish-owned "Drugstore" complex on the Left Bank in Paris in which two persons were killed and some 30 wounded.

In January 1975, he claimed responsibility in two attacks against Israeli El Al airliners here. In the first, he fired a bazooka-like weapon at the airliner but missed. In the second, he and accomplices commandeered the plane and flew it and their hostages to the Middle East.

On June 27, 1975, his luck almost ran out when he was surprised in the Left Bank apartment of a friend by a Lebanese informer and three agents of the Direction de la Surveillance du Territoire, French counterintelligence. He killed the Lebanese and two of the DST men, left a third badly wounded and escaped.