MOSCOW, April 13 — President Mikhail S. Gorbachev today gave President Wojciech Jaruzelski of Poland cartons of documents that the Soviet leader said “indirectly but convincingly” proved that the Soviet secret police killed thousands of Polish officers in Katyn Forest in the spring of 1940.

“It is not easy to speak of this tragedy, but it is necessary,” Mr. Gorbachev said. The Soviet Government has for the first time officially and publicly accepted responsibility for this long-denied crime of the Stalinist era, a massacre in the thick pine and birch forests west of Smolensk.

In response, General Jaruzelski said, “The Soviet statement about the crime of Katyn is, for our people, especially important and valuable from a moral point of view.”

“For us, this was an unusually painful question,” said the general, who is in Moscow on a state visit. On Saturday, he is scheduled to visit the clearing in the Katyn woods where a monument to the Polish officers was put up last year.

A Lift for Jaruzelski

The truth of what happened in the forests of Katyn has been, as Mr. Gorbachev said today, one of the “historical knots” that has complicated Soviet-Polish relations, particularly in the last year, as Eastern European countries have emerged from long domination by the Soviet Union.

Mr. Gorbachev’s admission of Soviet culpability in the killings during Mr. Jaruzelski’s visit could serve as a lift for the Polish President, one of the last Communist leaders to survive the turmoil in Eastern Europe, as he struggles to hold his position against a challenge by more liberal forces.

Some 15,000 Polish officers and others disappeared after they were handed over to the Soviet secret police when Soviet forces occupied parts of Poland in April and May of 1940. The occupation came as part of a secret Soviet-Nazi agreement at the outset of World War II.

The bodies of about 4,500 of those officers were unearthed in 1943 by Nazi troops after the Nazis captured the region. The German troops and several international commissions blamed the Soviets for the massacre after examining documents found on the dead officers and the uniforms that they were wearing when they were herded into the forest and shot. The 10,500 Poles who were not buried at Katyn vanished without a trace.

Move Toward Admitting Guilt

The men whose bodies were found in the mass graves in Katyn had all been shot in the head. The hands of many of the men were tied behind their backs, and many were bound, gagged and blinded by greatcoats flung or bound around their heads.

Polish investigators traveled to the forest to examine the bodies at the behest of the Polish government-in-exile in London after the Germans discovered the bodies in 1943. The investigators concluded that the Soviet Union was reponsible, but Stalin blamed Hitler. Eventually, Stalin broke relations with the London exile government, a move that led to the establishment of a Communist Government in Poland.

The Soviet side persisted until this year in blaming the Nazis for the crime, saying the killings took place in 1941, when the territory was in German hands. The inscription in stone that marks the spot of the killings says the officers were victims of fascism, shot by Hitler’s troops.

But it has been clear since last summer that Soviet officials were gradually moving toward admitting guilt for the killings, under pressure from journalists and historians who have uncovered incriminating evidence and from the Polish Government, whose previous Communist Government long conspired in blessing the official Soviet version of events.

Moscow’s ‘Profound Regret’

“After searching through the archives here and abroad, we came to the unmistakable conclusion that officers found at Katyn were shot and buried by Stalin’s secret police,” said Valentina S. Porsadnova, a member of the official Soviet-Polish commission set up two and a half years ago to resolve historical disputes between the counties. She said the commission’s conclusions on Katyn were to be published soon.

The official statement outlining the new Soviet position on Katyn, which was reported today by the official press agency Tass, expressed the Soviet Union’s “profound regret over the Katyn tragedy,” calling it “one of the gravest crimes of Stalinism.”

On Thursday night, Radio Moscow broadcast a report saying that the Soviet Union had officially accepted responsibility for the Katyn killings. The radio report said it was based on a statement carried by Tass. No such statement could be found on either the English- or Russian-language versions of the agency report.

Tass today denied having carried the report, and said Radio Moscow had somehow gotten hold of the official statement, which had been issued but which was not supposed to be made public until 6 P.M. today.

Evidence of Stalin’s Order

In his speech today at a Kremlin dinner honoring General Jaruzelski, Mr. Gorbachev said the soldiers and officers were killed by Lavrenty P. Beria, head of the Soviet secret police, the N.K.V.D., under Stalin, and by his associates.

A recent article in the weekly Moscow News said that although no document giving the direct order to shoot had been discovered, all the evidence indicated that it was Stalin who ordered the officers slain.

Natalya Lebedeva, the historian who wrote the article, said that Stalin was embarrassed by the Soviet defeat in the 1920 war against Poland and that he wanted to insure that the Poles could not end his control over them.

So when the Soviet Army occupied the parts of Poland accorded Moscow as part of its secret deal with Germany, Stalin ordered the N.K.V.D. to round up and jail Polish servicemen, she wrote, adding, “He apprehended those who might in the future enter the struggle for their country’s rebirth.”

Access Banned Until 1989

Moscow’s denial of Soviet involvement in the killings was so profound that the authorities did not even allow access to the site until last year.

Then a path was cleared through the towering forest to the raw spot where the mass grave had been discovered decades earlier, situated just outside the grounds of the secret-police rest house in the area.

“It is a place that speaks of the very depravity of Stalin and his clan,” said Mrs. Porsadnova. “Nobody who has ever been there can ever forget it.”

Photo: President Wojciech Jaruzelski of Poland, left, with President Mikhail S. Gorbachev of the Soviet Union after they met yesterday in Moscow. Mr. Gorbachev gave General Jaruzelski documents that Mr. Gorbachev said proved that the Soviet secret police killed thousands of Polish officers in World War II. (Agence France-Presse); Map of Soviet Union showing location of Katyn Forest.

Source: Ester B. Fein, The New York Times