This Communist state, evidently embarrassed by allegations of participation in the 1981 papal shooting and a variety of other illicit activities, has started cracking down on international drug and arms traffickers who have operated here for more than a decade.

In the new antismuggling campaign, Bulgaria in recent months has tightened spot checks at airports, land frontiers and seaports. The state-controlled press has trumpeted a series of arrests.

The effort appears to constitute indirect acknowledgement of past laxity in dealing with international criminal circles.

Revelations of Bulgarian wrongdoing have been spurred primarily by attempts to shed light on the inquiry into the attempt to kill Pope John Paul II. Bulgaria's role as a clearinghouse for Warsaw Pact weapons sales to friendly countries and to less ideologically compatible customers has received scrutiny that the Bulgarian authorities found unwelcome.

For instance, the international media in the past year has given prominence to charges by government officials and court investigators in Italy and Turkey that Bulgarians were involved in narcotics and arms smuggling partly aimed at destabilizing the two NATO countries. This pattern of politically motivated wrongdoing suggests that Bulgaria may have been willing to attempt the more dramatic crime of trying to silence the pontiff because of his support for the banned Solidarity union in his native Poland.

A desire to earn hard currency, however, evidently rivaled political goals in Bulgaria's illicit activities. Danish authorities have uncovered Bulgarian involvement in a smuggling ring funneling arms through South Africa to guerrillas battling the left-wing government of Angola. Likewise, Bulgaria supplied weapons to right-wing Christian militias in Lebanon until local communists asked it to stop.

Bulgarian authorities are noticeably ill at ease concerning these revelations, partly because they had hoped in recent years to forge another image abroad. Bulgaria's economy was improving from a low base, and authorities made a conscious effort to promote Bulgarian nationalism without unduly straining its traditional status as the Soviet Bloc's most obedient member.

Diplomats, intelligence analysts and Eastern European affairs specialists have theorized that Bulgaria's success in eluding large-scale exposure of its illicit dealings at home and abroad lulled it into a false sense of security.

Yet as long ago as 1972, columnist Jack Anderson disclosed the existence of a Central Intelligence Agency report alleging Bulgaria's importance as a "new center directing arms and drug trafficking between Western Europe and the Near East."

Anderson said Bulgaria was a "safe haven" for putting together major narcotics smuggling deals, that Bulgarian trucks were widely used for the trade and that even if caught smugglers were often let off with a light fine and their merchandise was returned.

The attempt on the pope's life--linked with other investigations in Italy--in the past year has focused the media's spotlight on charges of Bulgaria's unsavory roles in other fields.

An Italian magistrate has charged three Rome-based Bulgarian government employes with complicity in the shooting.

Suddenly dredged up from the past was the 1978 assassination in London of Bulgarian dissident Georgi Markov, who died after having been pricked by an umbrella equipped with a pinhead-sized platinum pellet containing a poison called ricin. Western intelligence sources say that the Bulgarian secret service planned the killing.

Also receiving prominence were revelations from Turkish documents indicating that Bulgaria sold arms to both left-wing and right-wing terrorist factions in Turkey before the military takeover there in 1980.

One well-documented case in 1977 involved a ship named Wasoula that Turkish customs authorities stopped in Turkish waters carrying 495 grenade launchers and 10,000 rounds of ammunition that had been loaded in the Bulgarian Black Sea port of Burgas.

In Lebanon in 1974 and 1975, just before the civil war, Bulgaria sold several shiploads of arms to right-wing Christian militias until the local Communist Party protested that the weapons would be used against its members and their left-wing and Palestinian allies.

Last winter Danish authorities uncovered a vast traffic that had been going on for years involving Bulgarian arms sales to Armscorp, the South African state arms firm. Bulgaria, they said, sold shiploads of Soviet Bloc weapons to South Africa, which passed them on to antigovernment rebels in Angola.

The investigations established that not only were Danish companies defying a United Nations ban on arms sales to South Africa, but also that Bulgaria was providing weapons for use against the Angolan government. Thousands of Cuban troops have been there for years as symbols of the Soviet Bloc's concern for that government's survival.

The Sunday Times of London alleged that the deal was arranged in Vienna by Ivan Slavkov, the head of the Bulgarian Olympic Committee, who once was married to the late daughter of Bulgarian Communist leader Todor Zhivkov.

Much of the arms business centers on Kintex, an official import-export firm headquartered in a Sofia building that is off limits to foreign diplomats accredited to Bulgaria.

Kintex is close to the Hotel Vitosha-New Otani, Sofia's most expensive hostelry. It was favored by rich Arabs, Turkish smugglers and other well-heeled travelers, but the adverse publicity from the "Bulgarian connection" drove the less savory characters away last fall.

The pope's would-be assassin, Turk Mehmet Ali Agca, stayed in the hotel in July 1980 at the same time as a prominent Turkish smuggler, Bekir Celenk, charged as a key accomplice in the shooting.

Although Bulgarian officials have suggested privately that they were duped in many of these affairs, the cases do little to bolster Bulgarian claims that the CIA has invented the "Bulgarian connection" in an attempt to distract attention from western unemployment, inflation and the controversial stationing of U.S. nuclear missiles in Western Europe.

Bulgaria's official press has insisted--despite vast evidence to the contrary--that Bulgaria had nothing to do with Turkish smugglers.

"Neofascist terrorist movements, organizations and gangs of the Gray Wolves type, their activities and their supporters have nothing to do, nor could they possibly have anything to do, with socialist Bulgaria or with any socialist country for that matter," BTA, the official Bulgarian news agency, said on Nov. 30, four days after the arrest in Rome of Bulgarian state airline official Sergei Antonov as an accomplice in the papal shooting. The Gray Wolves was a terrorist group of which Agca was a member.

The Bulgarian authorities have held news conferences and distributed statements and booklets--including a 107-page brochure entitled "Anatomy of a Slander Campaign"--to press their case.

Bulgarian officials recalled, for example, that in 1978 they handed to the Bonn government four West Germans said to be members of the Baader-Meinhoff terrorist gang.

They have likened their plight to the Nazis' disputed charges against Georgi Dimitrov, the founder of Bulgarian communism, who was accused of burning down the parliament building in Berlin in 1933.

Just as the Nazis themselves purposely set that fire, so the authorities here now argue, the CIA is responsible for the present furor. The CIA, according to the Bulgarian argument, invented the "Bulgarian connection" as part of President Reagan's anticommunist crusade.

Some analysts are convinced that the Bulgarians indeed were involved with Agca and his smuggling and Gray Wolves contacts, but that the attempt to kill the pope was of his own doing. They find it unlikely that Bulgaria would have been so foolish as to get involved in such an amateurish operation, or at least one along the lines that Agca is said to have described.

Some diplomats, nonetheless, point to the growing number of prominent Bulgarians, including an ambassador to Czechoslovakia and the manager of a major Sofia hotel, whose fondness for foreign currency led them to compromise promising careers and landed them in jail.