The Italian prosecutor in the case against a Bulgarian airlines official accused of complicity in the 1981 papal assassination attempt today recommended against releasing the man from prison, according to judicial sources.

The finding rejected a defense petition to free Sergei Ivanov Antonov based on defense evidence attempting to establish Antonov's alibis for May 13, 1981, the day of the shooting of Pope John Paul II in St. Peter's Square, and the two preceding days.

Antonov's release would have been a significant blow to government efforts to establish a so-called Bulgarian connection to the assassination attempt based on information provided investigators by Mehmet Ali Agca, a Turkish terrorist who was convicted of the shooting.

The chief investigator in the papal shooting, Judge Ilario Martella, will make the final decision on Antonov's release within 10 days, but it is not considered likely he will act against the finding of the other judge, Rome magistrate Franco Scorza, unless there are new developments in the case.

Defense lawyers Giuseppe Consolo and Adolfo Larussa said today they would await Martella's ruling before making any comment.

The defense petition, filed Jan. 4, asked for Antonov's release on grounds of an "absolute lack of evidence" and alibis provided for Antonov by at least eight Bulgarian and Italian witnesses. The petition and its accompanying evidence gave rise to speculation that that the charges against Antonov might be dropped.

Judicial and legal sources said Scorza's negative opinion could reflect either knowledge of as yet undisclosed evidence against Antonov or questions about the reliability of some of the defense witnesses.

The sources also pointed out that Scorza had asked for and received an extension in the deadline originally set for his reply so that he could examine further evidence. Last week, Scorza and Martella carried out what was believed to be a first inspection of Antonov's two-room Rome apartment, according to press reports, to check the apartment against Agca's description of the place he claims he met Antonov.

Another Turkish suspect in the case, Musa Cerdar Celebi, was extradited to Italy from a West German prison last Friday.