A Soviet citizen whose disappearance in Brazil two weeks ago triggered a spate of rumors of spying and murder has requested asylum in the United States, the Brazilian and U.S. governments announced today.

Sevim Gueraibekov, 32, a dark-haired, outgoing man attached to a delegation of 48 Soviet political scientists in Brazil for a conference, vanished from the Rio Copa Hotel in Rio de Janiero nearly two weeks ago, one day before his group was to return to Moscow.

U.S. Embassy spokesman Don Hauger said in Brasilia that Gueraibekov had requested U.S. asylum and was temporarily staying in a third country, The Associated Press reported.

In Washington, State Department spokesman Joe Reap said Gueraibekov's application will "be processed in accordance with U.S. law and policy governing the admission to this country of refugees." He declined to elaborate.

A spokesman at the Soviet consulate in Rio said there was no official word on the case from the Soviet Embassy, AP reported.

Gueraibekov's disappearance prompted a flurry of speculation in Brazil's newly unrestricted press, and the rumors were complicated when a body resembling Gueraibekov's was found with marks of strangulation near a polluted canal in an industrial district 45 miles from Rio.

As Brazilian witnesses delivered opposing judgments on whether the body was Gueraibekov's, Brazilian police fumed and commentators rushed to the archives of spy lore for comparison. Martin Cruz Smith's "Gorky Park," the thriller of Soviet spies and unidentified bodies, rose a notch to number seven on the Brazilian best-seller list.

But the most uncomfortable public actors in the drama were U.S. diplomats here, who repeatedly refused to clear up at least part of the mystery by confirming or denying that the Soviet had sought U.S. asylum.

That stony silence encouraged a plethora of reports in diplomatic and media circles. Several stories maintained that the missing Soviet was whisked out of the country by U.S. officials, possibly without the knowledge of Brazilian authorities. Another account this week said that Gueraibekov was spotted meeting with U.S. officials but disappeared before asylum could be arranged.

"In reality, the traditional roles of the two superpowers seem to have been reversed," commented the news magazine Veja this week. "While the Soviets go out on the streets, make statements, receive the press and answer questions, the American side shuts all the doors."

The mystery was deepened by the figure of Gueraibekov, who was described by the Soviets only as a tourist accompanying the political scientists.

United Press International quoted diplomatic sources in Brazil as saying he may have been a security officer assigned to watch the Soviet participants in the conference.

At the Rio Copa Hotel, dressed in shorts and holiday shirts, Gueraibekov flirted with waitresses in the restaurant--presenting one with a gift of caviar--and lauded Rio and its beaches to the hotel manager. But the manager later said to the press that "he looked very tired as if he had not slept at night."

When Gueraibekov disappeared, diplomats and journalists quickly assumed that he had taken refuge in the U.S. Consulate in Rio, and a report appeared saying that he had been spotted entering the door.

But that was before Brazilian police found the body of a man apparently beaten and strangled in the suburb of Santa Cruz, and they were unable to match his fingerprints with those of any Brazilian citizen in the state.

Brazilian investigators conceded that the body could be Gueraibekov's, and the Rio Copa Hotel manager announced after seeing the corpse that he was "90 percent sure" it was the mysterious Soviet tourist.

Just as the disappearance appeared to have become a political assassination story, though, a Rio Copa waitress arrived to view the body and announced to excited reporters outside that it was definitely not Gueraibekov.

"He adored the beach and the night life of Rio, and so I think he wanted to escape the Iron Curtain," she announced.