The Turkish gunman who tried to assassinate Pope John Paul II refused today to give evidence against his alleged Bulgarian accomplices, claiming that he had received death threats from Soviet Bloc security services.

In a day of sometimes contradictory testimony, Mehmet Ali Agca described in detail how he had spent nearly two months in Bulgaria in the summer of 1980 but omitted earlier statements about discussing plans to assassinate the pope with members of the Bulgarian secret service.

He also said he had "invented" parts of an account he gave to an Italian magistrate who spent three years investigating allegations of an elaborate Soviet Bloc conspiracy to kill the Polish-born pontiff.

Pressed to specify which parts of his pretrial testimony were true and which false, Agca refused to go into detail. Immediately after a lunch break, however, he surprised the court again by announcing with a rhetorical flourish in Italian: "With a clear conscience, I confirm everything. Bulgaria is guilty."

Agca's erratic behavior produced a day of high drama in the courtroom, with moments of extreme tension alternating with general laughter. The presiding judge, Severino Santiapichi, was involved in several shouting matches with both prosecuting counsel and defense lawyers as he sought unsuccessfully to persuade the pope's assailant to answer his questions.

Much of the prosecution case against the three accused Bulgarians rests on Agca's pretrial testimony. Only one of the three, the former deputy director of Bulgarian state airlines in Rome, Sergei Antonov, is present in court. No independent witnesses have been found so far to support Agca's allegations about a series of meetings with the Bulgarians in Bulgaria and Italy in the months leading up to the shooting in St. Peter's Square on May 13, 1981.

Pressed to explain his refusal to give evidence against the Bulgarians, Agca gave explanations ranging from an alleged political deal hatched between the Vatican and Bulgaria to purported threats from the Bulgarian secret service and the Soviet secret police, the KGB. He also repeated earlier claims that he was "Jesus Christ."

Asked to give the court examples of such "threats," Agca cited a letter he received from a Bulgarian judge warning him that he could be put on trial in Sofia for the alleged crime of slandering the Bulgarian people. He also accused a Bulgarian judge who cooperated in the Italian investigation of threatening him.

"The Bulgarian magistrate told me I had damaged the Soviet Union -- and would be made to pay in one way or another," Agca said in a remark that provoked furious protests from Italian defense lawyers representing the accused Bulgarians.

Agca's claims were contested by a Bulgarian magistrate, Jordan Ormankov, who was allowed to attend some of the Italian interrogation sessions in October and December 1983. Ormankov said that half a dozen Italian officials were present at all the sessions and that there was no opportunity to talk to Agca directly.

During the first two weeks of the trial, Agca has made general accusations against the Soviet Union, Bulgaria and Syria and has named several Turkish right-wing militants as his accomplices. He refused to give testimony on the second day of the trial -- saying that he was waiting for a signal from the Vatican to his claims to be Jesus Christ -- but has behaved more or less normally since.

Today's session began with the judge questioning Agca about a note that was found on him on the day of the assassination attempt. The note appeared to contradict his subsequent attempts to present himself as "a terrorist without ideology" who had agreed to shoot the pope in return for the equivalent of $1.2 million by the Bulgarian secret service. The mercenary motivation has been accepted as accurate by an Italian state prosecutor.

Agca acknowledged writing the note, which described the attempted murder of the pope as a protest against "the killings of thousands of innocent people by dictatorships and Soviet and American imperialism," and said it reflected his views. He added that he had acted for a "personal motive" in shooting the pope.

Clearly concerned by Agca's refusal to confirm that he had shot the pope for money, as alleged in the public indictment, Santiapichi then asked him to confirm his earlier testimony about the involvement of the Bulgarians. When Agca insisted that the story was "complicated," the judge suggested that he tell it in his own words.

Speaking in Turkish through an interpreter, Agca then described how he had sought refuge in Bulgaria in the summer of 1980 after escaping from a Turkish military prison in November 1979. He said he had been protected in Bulgaria by Abuzer Ugurlu, a prominent Turkish smuggler with links to the Bulgarian authorities, who supplied him with a false Indian passport.

Tension rose as Agca recounted his stay in the Bulgarian capital of Sofia without mentioning crucial meetings at which the plot to kill the pope allegedly was hatched. In pretrial testimony, he told Italian magistrates that the meetings were attended by a Bulgarian Embassy official in Rome, Todor S. Aivazov, and a Turkish businessman, Bekir Celenk, who has been accused of being the plot's paymaster.

Aivazov and Celenk, who are both in Bulgaria, are on trial in absentia.

After Agca completed the Bulgaria portion of his story without mentioning his alleged Bulgarian accomplices, public prosecutor Antonio Marini shouted at him to tell the court about the meetings he had held in Sofia. The first of several rows then ensued between the prosecutor and the judge, who wanted to allow the Turk to continue telling his own story.

After a break, Santiapichi pressed Agca to state simply whether his allegations against the Bulgarians were true or false.

"I cannot say whether they are true or not," the papal assailant replied. "There is a political background to this."

Agca then cited a meeting held in the Vatican on May 24 -- three days before the trial opened -- between Pope John Paul and a Bulgarian delegation. Insisting that "the Vatican is in the middle of all this," he said the pope had agreed that a Slavic people could not be slandered.

(The pope's words, as reported by the Italian news media, to which Agca had access, were that he prayed for a "positive solution" to the trial so as not to harm the good name of a Slavic people.)

Agca then claimed that he had been told by the Vatican that he was Jesus Christ. "I am both an accused and Jesus Christ," he said. "The two things are not incompatible."

Asked by the judge to say whether he told the truth to investigating magistrate Ilario Martella, who was responsible for preparing the case for trial, Agca replied: "I said some things that were true and some other things that were invented."

During the afternoon session, the judge read Agca portions of his final cross-examination in February 1984 by Martella and asked him if they were true. After some hesitation, Agca said he confirmed what he had already told the magistrate.

The trial was adjourned until Tuesday.