Sergei Antonov, one of three Bulgarians accused of having plotted the attempted assassination of Pope John Paul II in 1981, told a Rome court today that he is an "innocent man."

Testifying for the first time in the papal conspiracy trial, Antonov, the former deputy director in Italy of Balkanair, the Bulgarian state airline, vehemently denied any involvement in the papal shooting. He claimed never to have known Mehmet Ali Agca, the Turk who has been convicted of shooting the pope in St. Peter's Square on May 13, 1981.

It is on the basis of Agca's often-changing testimony from jail, where he is serving a life sentence, that Antonov, two Bulgarian diplomats, and four other Turks are on trial here for allegedly plotting and aiding the assassination attempt.

Antonov, who celebrated his 37th birthday today, is the only Bulgarian in Italian custody. The two diplomats left Italy for Bulgaria before they could be arrested. Citing diplomatic immunity, they have since refused to return to Rome to stand trial. The two diplomats and two of the Turks, who were also indicted but who are not in Italian custody, are being tried in absentia.

"I want to say [to you] that you have in front of you an innocent man," Antonov said through an interpreter, as he sat before the two-judge and six-jurist court. Antonov had been brought out of the gray steel-barred cage from where he has been quietly watching the preceedings since the trial began May 27.

His testimony was solicited by Judge Severino Santiapachi to try to establish the veracity of claims made by Agca, who has been testifying before the court for 17 days. Agca has claimed that Antonov and the other two Bulgarians, Todor Aivazov and Zhelio Vasilev, drove him and a Turkish accomplice, Oral Celik, to St. Peter's square for the attack on the pope. He testified that Antonov was supposed to have driven a getaway car for the two Turkish assailants after the shooting.

"I never saw, I never met with the person who accuses me," Antonov said, as Agca, sitting in a chair some six feet away, tried to interrupt by crying out, "I must also speak." Judge Santiapachi told him he would have a chance after Antonov's testimony.

"For two years and six months I have been away from my country, my family, my friends, my colleagues, because of the absurd, slanderous accusations of a person I have never met," Antonov said.

The Bulgarian airline official testified that on the the day of the shooting, he was working in his Rome office -- an alibi that previously was called into question by the investigating magistrate whose report ultimately led to this trial.

Under questioning by Judge Santiapichi, Antonov also denied he had ever used the code name "Bajramic" as Agca had claimed and said that he had never been a member of the Bulgarian secret police or been trained in terrorism.

After Antonov finished his testimony, Agca called the Bulgarian's testimony a "political speech to touch the sentiments of the court."

Turning to face the court audience, which consisted mostly of defense lawyers and journalists, Agca said excitedly: "I have nothing against Antonov. I have nothing against the Bulgarian people . . . [but] Antonov is guilty."