Italy, Bulgaria -- and the hand of the KGB?

Numerous revelations in the last few days have bolstered investigators' suspicions that Bulgarian agents may have been involved not only in the shooting of Pope John Paul II last year but also for several years in a conspiracy against the Italian democratic system.

The suspicions have led to an unproven supposition here that the KGB - the Russian spy agency formerly led by Soviet leader Yuri Andropov - tried to influence the crisis in Poland by arranging the 1981 assassination attempt on the Polish-born Pope through Bulgarian agents. The latest evidence suggests at least that Bulgarian agents, operating in Italy, sought to undermine the Polish independent trade union Solidarity.

The new developments have seriously strained Italian-Bulgarian relations. The two countries have called back their ambassadors in a growing crisis that may have wider repercussions in East-West relations. The subject most likely came up during United States Secretary of State George Shultz's visit with the Roman Catholic Church leader at the Vatican Dec. 13 and with Italian officials.

Nearly three weeks ago Italian police arrested the manager of Bulgaria's Balkan Airlines office in Rome, Ivanov Antonov, who was identified by the Pope's would-be assassin Mehmet Ali Agca as one of his Bulgarian accomplices. Investigators are also seeking two more Bulgarians who recently reached safety in their country, the secretary to the military attache at the embassy in Rome, Vassiliev Kolev, and embassy cashier Teodoro Ayvazov.

(In Sofia, the Bulgarian government called the charges against the two embassy officials ''absurd,'' and claimed it was conducting its own probe into the shooting of the Pope, according to the Bulgarian press agency.)

Italian investigations into what is believed to be a Bulgarian connection took a new turn after the confession of jailed Italian trade union leader Luigi Scricciolo, who ran the international relations bureau of the major labor group Unione Italione del Lavoro (UIL), and who kept contacts with unions throughout the world, including the AFL-CIO.

Scricciolo has revealed to Italian police that he worked for the Bulgarian secret service, which instructed him to spy on Solidarity, on Lech Walesa, and on the Polish union's international funding.

Scricciolo was the first Western trade unionist to visit Poland after the creation of Solidarity. He won the trust of Solidarity leaders and personally organized Walesa's visit to Rome in January 1981.

Investigators believe that throughout his numerous trips to Poland, the UIL official played a key role - halfway between a spy and an ''agent provocateur'' - in a plan to undermine Solidarity and that the information he delivered to Bulgarian agents was used to wage a campaign to discredit the Polish union and justify repression.

UIL secretary general Giorgio Benvenuto has accused his former aide of having infiltrated the union several years ago. Scricciolo is believed to have supplied Bulgarian agents with lists of names of Polish union leaders and their contingency plans if Solidarity had to go underground, which could partially explain the effectiveness with which the Jaruzelski regime shut down the union a year ago.

Scricciolo has only recently decided to speak out, apparently to take advantage of a new Italian law which allows plea bargaining.

He was arrested in February on charges of aiding the Red Brigade kidnappers of US Brig. Gen. James L. Dozier. He admitted he was a liaison between the Red Brigades and Bulgarian agents whom he supplied with the text of Dozier's interrogation by his captors.

Scricciolo also confessed that on numerous occasions he had put Bulgarian agents in contact with Red Brigades leaders. This latest revelation is seen here as concrete evidence of Italian President Sandro Pertini's repeated allegations that the Italian terrorist wave of the last decade had international roots and was part of a broader plot to destabilize democracy in Italy.

In fact, the Bulgarian connection is turning up in other investigations in Italy. A two-year probe in Milan broke up the biggest arms and drugs ring ever discovered in Europe. Police arrested 241 suspects.

Investigators charge that the Bulgarian capital of Sofia was a meeting point where Middle East drug dealers, international terrorists, Mafia bosses, and Turkish organized crime leaders used drugs as payment to buy and sell heavy weapons, including tanks and helicopters. A similar conclusion has been reached in Palermo, where another arms-drugs racket has been uncovered.

It has been revealed that Ali Agca visited Sicily six months before the shooting in St. Peter's Square and is believed to have had contacts with Mafia suspect Salvatore Panzera, in whose home large sums of Bulgarian currency were found.

The name of Bekir Celenk, suspected ''Turkish Mafia'' boss, has cropped up in two of the investigations. Agca claims that in a meeting in Sofia Celenk offered more than $1 million to shoot the Pope. Celenk, who has lived in Sofia's most luxurious hotel for years, is sought by both Italian and Turkish authorities for gun running.

Since both Scricciolo and Agca decided to talk, numerous Bulgarian diplomats have quietly returned to their country (including Kolev and Ayvazov).

The Italian Parliament will meet in a special session this week to discuss more radical diplomatic moves against Bulgaria. The policy of ''appeasement'' has broken down, and Sofia and Rome appear to be on a collision course.

The Italian Foreign Ministry was concerned about the political implications of the Bulgarian connection, which many experts claim leads directly to the Soviet KGB.

The former chief of the Bulgarian secret service, Stefan Sverdlev, who defected to the West three years ago, asserts that Bulgarian agents are so closely linked to the KGB that every Bulgarian espionage department takes orders from Soviet officials.

In an interview with French television, Sverdlev said he does not ''for an instant doubt'' that Bulgarian agents were involved in the assassination attempt but that they could do so only on instructions from the KGB, and that the go-ahead for such an operation could have been given only by Andropov and, ultimately, by Leonid Brezhnev.