An Italian prosecutor called today for the acquittal of three Bulgarian officials charged with plotting to assassinate Pope John Paul II, saying there was insufficient evidence to convict them.

The prosecutor's request came near the end of a nine-month trial of the alleged accomplices of Mehmet Ali Agca, a Turkish gunman who shot and seriously wounded the Polish-born pope in St. Peter's Square in May 1981. The prosecutor asked that the three remaining Turkish defendants be convicted and sentenced to prison terms ranging from 20 years to life.

In the view of Italian legal experts, there is now little likelihood of the Bulgarian defendants being found guilty, even though the eight-man court is not obliged to follow the prosecutor's recommendations. Final verdicts in the case are expected by the end of March after closing pleas by defense counsel.

Allegations of Soviet Bloc involvement in the plot to kill the pope ignited a worldwide controversy over the Kremlin's role in international terrorism and at one point appeared to cast a shadow over the future of East-West relations. Much of the heat, however, has gone out of the debate over the past few months in view of the difficulty of finding evidence to convict the Bulgarian defendants.

Last year, a preliminary report by another Italian prosecutor linked the papal assassination attempt to concern in the Soviet Bloc over political upheavals in Poland in 1980-81. The report speculated that a decision to kill the pope had been made by a Communist "politician of great power" to remove the religious inspiration for Poland's independent Solidarity trade union.

Interest in the present proceedings, which the Italian press initially dubbed "the trial of the century," waned rapidly as Agca, the prosecution's star witness, repeatedly undermined his own credibility. The pope's would-be assassin, who stunned the court on the trial's opening day by claiming to be Jesus Christ, has retracted testimony and admitted that he lied to his interrogators on several occasions.

Before making his concluding recommendations, Prosecutor Antonio Marini criticized the court for turning down several requests to hear further witnesses who, he suggested, could have supported the state's case against the Bulgarian defendants. He also criticized the Bulgarians' alibis for the day of the shooting as contradictory and unsupported by independent evidence.

The prosecutor's attempts to introduce new evidence were overruled by Presiding Judge Severino Santiapichi on the grounds of irrelevance. The judge, one of Italy's most experienced magistrates, is reliably reported to have privately expressed exasperation at the length of the proceedings and the wildly differing testimony provided by more than 100 witnesses.

The only Bulgarian defendant in Italian custody, Sergei I. Antonov, was not present in court when the prosecutor made his final recommendations. The former Balkanair official has exercised his legal right to stay away from the trial for the past six months, arguing that he is sick and depressed.

The two other Bulgarian defendants, Col. Zhelyo K. Vasilev and Todor S. Aivazov, returned home in 1982 before warrants were issued for their arrest on the basis of Agca's pretrial testimony. Both defendants refused to come to Rome for the trial, pleading diplomatic immunity, but were questioned by the court in Sofia in December.

Antonov's Italian defense lawyer, Giuseppe Consolo, expressed satisfaction at the prosecutor's request but said he would call for his client's complete acquittal. Under Italian law, there is a distinction between acquittal "for lack of proof" -- which leaves some doubt about the guilt or innocence of the accused -- and a full acquittal on the grounds of proven innocence.

The prosecutor called on the court to impose life sentences on Musa Serdar Celebi, the leader of a right-wing Turkish emigre organization, who has been accused of providing logistical support for the assassination attempt. Marini demanded a similar sentence for Oral Celik, a leader of Turkey's right-wing Gray Wolves group and one of Agca's closest associates, who was tried in absentia on charges of taking part in the shooting.

Marini said that Omer Bagci, a second-string Gray Wolf who has confessed to smuggling Agca's pistol into Italy, should be sentenced to 20 years' imprisonment.

A fourth Turkish defendant, Bekir Celenk, died of a heart attack during the trial, shortly after returning to Turkey from Bulgaria. A businessman with underworld connections, Celenk was accused of paying the Gray Wolves the equivalent of $1.2 million to shoot the pope on behalf of the Bulgarian secret services.

During his summing up, Marini repeatedly referred to the trial as "truncated" because of the impossibility of interrogating Celenk and other key witnesses. His complaint about Celenk was, however, brushed aside by the judge who said, amid laughter: "It's not our fault if Celenk died. People have a habit of dying."

Antonov's defense lawyers said today they will attempt to prove that Agca was fed incriminating details about the Bulgarian defendants when they make their concluding pleas to the court next week. Communist propagandists have consistently claimed that the so-called "Bulgarian connection" to the assassination attempt was fabricated by western intelligence services, but have been unable to document this charge.