By FABIOLA SANTIAGO

Gustavo Castillo -- an anti-Castro militant jailed in Mexico for his alleged role in an attempt to kidnap a Cuban diplomat -- is back in Miami, a free man.

Friday, two days after Mexican authorities released him and allowed him to return to the United states, Castillo went on the air on two Spanish-language radio stations. He thanked the Cuban exiles who donated hundreds of thousands of dollars for his defense and that of Gaspar Jimenez, who remains in a Mexican jail in connection with the same incident.

Callers to one station hailed Castillo as a hero of the anti-Castro movement.

Last year, Castillo and Jimenez were extradited to Mexico, where they were convicted of charges related to the 1976 attempt to kidnap Cuban consul Daniel Ferrer in Merida, Mexico. Ferrer's bodyguard Artagnan Diaz was shot dead during the attempt.

Castillo received a nine-year sentence, later reduced to six.

He was released ahead of time because he served three years in the United States while awaiting extradition, and because he earned time for prison-work in Mexico. Castillo said.

But he is bitter about his imprisonment. He insists he committed no crime.

"When the United States government supported us the anti-Castro militant exiles, we were called the freedom fighters," Castillo said in an interview Friday. "After the government abandoned its support, immediately, they began calling us terrorists."

"I am a freedom fighter," he said. "1 don't want to be called a terrorist. I want to see my homeland free, and I want to find the ways to win its freedom."

Castillo said Jimenez, who is serving a sentence similar to his own. may also be freed soon. A Mexican prison official who asked not to be named confirmed Jimenez's pending release. A third exile charged in connection the Merida incident, Orestes Ruiz, also remains in a Mexican prison, serving a 32-year sentence.

Both Jimenez and Castillo fought their extradition to Mexico for three years. During most of that time, they were jailed at the Federal Correctional Institution in Homestead.

Before the men were arrested in January 1978, Castillo had been subpoenaed to appear as a witness in grand jury investigations of Miami-based terrorist activities.

In 1977, he was charged and later acquitted of the bombing of the University of Miami Student Union before black-activist Angela Davis was scheduled to speak there.

Castillo's freedom is a dream come true for his mother, Laura Perez. She worked tirelessly to raise funds for his release, joining efforts with other supporters who led radio marathons to collect money for her son's defense.

Friday night, at her Hialeah home, the telephone rang constantly. In the kitchen and living room, friends and family chatted about lighting a Christmas tree. Castillo announced he is looking for a girlfriend.

"I'm 36 and available," he joked.

During Friday morning newscast on WQBA, commentators invited listeners to call in and talk to Castillo. News director Armando Perez Roura, who was active in the campaign to free Castillo, said the station was flooded with calls.

One woman said that she had just arrived in Miami from Cuba via Costa Rica when she heard about the efforts to collect money for Castillo.

"Any mother is capable of doing: what I did," Perez said Friday night. "Now, I have to go to church often and pray, because it was really God who brought my son back."

Herald staff writer Jim McGee contributed to this report.