Yeltsin Tells of Soviet Atrocities : Legacy: Russian releases documents on 1983 downing of KAL jetliner and the mass murder of Polish officers in WWII. Gorbachev is blamed for suppressing secrets.

Shedding new light on the bloody legacy of Soviet communism, Russian President Boris N. Yeltsin on Wednesday revealed documents on two of its most heinous acts: the downing of a South Korean jumbo jet and the World War II mass murder of thousands of Polish officers.

Yeltsin called the 1983 willful destruction of the Boeing 747 “the most horrible catastrophe of the Cold War.” He said Russia regards it as a “holy duty” to make all the facts known--including secrets contained in the doomed jet’s flight recorder.

Yeltsin and his spokesmen also went out of their way Wednesday to put their revelations in a more immediate political context: They blamed former Soviet leader Mikhail S. Gorbachev, Yeltsin’s longtime political rival and now an irritating and persistent critic, for keeping such explosive, embarrassing material secret for so long.

In the Kremlin, Yeltsin received a South Korean delegation headed by Deputy Transport Minister Chang Sang Hyon and handed over 12 previously secret documents relating to the destruction of the Korean Airlines Anchorage-to-Seoul flight by a Soviet interceptor over Sakhalin island on Sept. 1, 1983.

Yeltsin, in a separate ceremony, delivered the same files to U.S. envoys and was thanked by Ambassador Robert S. Strauss. Yeltsin said he also received a message of gratitude from President Bush.

All 269 people aboard KAL Flight 007 were killed, including 61 Americans, when the Soviet MIG fired two missiles at it.

The raft of documents made public more than nine years later includes a full transcript of the magnetic tape from the jetliner’s flight recorder, Yeltsin said.

Also handed over were: texts of recordings from on-board intercoms; transcripts of conversations with other aircraft and ground control stations; reports by then-Soviet leader Yuri V. Andropov; findings by the Soviet Defense and Aviation ministries and KGB; photographs of wrecked sections of the Boeing, and a map of KAL 007’s flight path.

For his government to reveal such materials was “not a simple decision, but a necessary one,” Yeltsin said. “All leaders of the former (Soviet) Union for the past 10 years knew about this, but hid the documents from international opinion,” he added, delivering a transparent accusation against Gorbachev.

To make the point further, Vyacheslav V. Kostikov, Yeltsin’s press secretary, emphasized that the man whose name once epitomized Moscow’s desire for openness knew the flight recorder had been recovered by Soviet searchers from the KAL flight, but kept silent.

Yeltsin’s fulfillment of a promise he made at the Washington summit last June to declassify KAL-related documents drew immediate praise from U.S. officials and the families of victims, some of whom attended the Kremlin ceremony.

“It is a courageous act of President Yeltsin,” said Hans Ephraimson-Abt, who lost his daughter Alice, 23, and is a spokesman for American relatives. “We think it is also a great gesture of his that Russia is joining the international community, in that despite political opposition, they are willing to address unpopular issues.”

“We are delighted,” one U.S. official commented. “We stand firmly behind the families; they have a right after nine years to know what happened to the remains of their loved ones, to their personal effects, to seek financial compensation from the Russian government.”

The families thus far have pursued multimillion-dollar claims chiefly against the airline; it was unclear immediately how the documents released Wednesday might affect their case.

Also Wednesday, a Russian official sent to Warsaw made public for the first time copies of documents signed by Soviet dictator Josef Stalin ordering the mass murder of 14,700 Polish officers in the Russian forest near Smolensk 52 years ago.

Polish President Lech Walesa’s voice shook as he received the two beige cardboard files from Rudolf Pikhoya, Yeltsin’s personal envoy. “We are witnessing the handing over of the most important documents concerning the cruel crime against the Polish nation,” Walesa said. “My legs are trembling.”

As well as documenting the Kremlin’s direct responsibility for what is known as the Katyn massacre, the files also include orders to execute 11,000 Poles who were held in Soviet prison camps. The most incriminating papers, dated March 5, 1940, chronicle the ruling Politburo’s vote, led by Stalin, in favor of the mass executions.

It was only in April, 1990, or more than five years after Gorbachev became general secretary of the Soviet Communist Party, that the Kremlin admitted for the first time that the Stalin-era NKVD secret police, and not the Nazis, were responsible for the Katyn massacre.

But Wednesday was the first time the existence of the direct Politburo order was disclosed. Kostikov charged at a news conference in Moscow that Gorbachev had continued to “camouflage” the truth about Katyn and said the documents handed to Walesa came from a secret Central Committee file that had been in the Soviet presidential archive.

“The respected Mikhail Sergeyevich long ago--many years ago--knew of the tragedy and the true identity of the guilty ones,” Kostikov, waving memos stamped “Top Secret,” said. “But he remained silent.”

Such documents may be introduced into evidence at the Russian Constitutional Court’s hearing on the deeds of the Soviet Communist Party, at which Gorbachev has refused to testify, Kostikov added.

Gorbachev’s tug of war with Yeltsin over his civic duties and right to leave the country has caused a recent revival of sympathy abroad for the former Soviet president. But Wednesday’s revelations can only harm his world standing.

Gorbachev also was dealt an unexpected defeat by judges of the Constitutional Court, after what seemed to be a truce in his war of wills with Yeltsin. The tribunal decided Wednesday that he could not go to Italy as he had planned until he appears in court; the justices earlier had said he could be issued a passport to attend former West German Chancellor Willy Brandt’s funeral on Saturday.

Gorbachev was forced to cancel the Italy trip. Georgy K. Shakhnazarov, his close aide, protested that Gorbachev had received telephone assurances from Valery D. Zorkin, the chief justice of the court, that he would be allowed to go. Shakhnazarov accused Yeltsin of intervening in the meantime to humble Gorbachev and force him into exile abroad.

Viktor K. Grebenshikov, a reporter in The Times’ Moscow Bureau, contributed to this report.