MOSCOW -- The Soviet Union ended a half-century of denials Friday and officially admitted Josef Stalin's secret police killed 15,000 Polish officers held prisoner during World War II. Poland welcomed the Kremlin's apology as a first step toward healing old wounds.
'Thousands of Poles have waited for this information for 47 years,' Polish radio said.
Soviet President Mikhail Gorbachev turned over documents to Polish President Wojciech Jaruzelski that showed the Soviets had killed the officers in what is known as the Katyn Forest massacre.
'The discovery of the archival material allows us to conclude the direct responsiblity for the atrocities of the Katyn Forest lies with (security police head) Lavrenti Beria and his henchmen,' the official news agency Tass said.
'The Soviet side expressed profound regret over the Katyn tragedy, declaring that it was one of the most heinous crimes of the Stalin era.'
Jaruzelski, who travels to Katyn Saturday to end his four-day official visit, said he was pleased the Soviets had finally acknowledged their responsibility for the killings.
'I think these documents will be a very valuable help to historians, not to mention of great value to the families,' he said.
It was the first time the Soviet Union has officially admitted the slaughter of the Polish officers -- an incident that has soured relations between the two countries for 50 years.
For years Moscow officially blamed the Nazis for the massacre.
'It is good when the murderers confess their crime,' Polish Solidarity leader Lech Walesa said from Gdansk after the announcement. 'But the murderers must remember that this is only half the problem. Material compensation for wrongs done to the families of victims ... still remains a problem.'
Tass said Soviet historians discovered documents showing that Polish officers, taken prisoner as the Soviets moved into Polish territory under Stalin's non-aggression pact with Adolf Hitler, were held in camps by the NKVD, the wartime Soviet security service.
'The documents show that in April and May of 1940, 15,000 Polish officers that were in these camps were taken out,' Tass said. 'Three hundred ninety four people were transferred to Gryazovetsky concentration camp but the main portion were transferred into the hands of the NKVD.
'There was never again any mention of them,' the dispatch said.
About 4,000 of the officers were found in mass graves in the Katyn Forest in the western Soviet Union. The remaining 11,000 bodies were unaccounted for.
For years, Poles were afraid to broach the subject of the Katyn massacre, but with the rise of Solidarity in 1980 they started speaking out and openly commemorating April 3, 1940 -- the anniversary of the slayings.
After Gorbachev set up a special commission in 1986 to investigate Katyn and other 'blank spots' in Polish-Soviet relations it was only a matter of time until the Soviets admitted responsibility.
Poles and independent historians have claimed since the end of World War II that the Soviet secret police killed the Polish officers.
In the last month Soviet publications have printed evidence of the NKVD's involvement, including lists of officers involved, routes used to move the prisoners and other details, but the Kremlin had remained silent.
Moscow Radio's English-language service got a little ahead of the official apology during a broadcast Thursday night in which it broke the story, but then did not repeat the broadcast until the official Tass announcement Friday afternoon.
Jaruzelski began the trip in Lvov, a former Polish city in the western Ukraine. He also visited Kiev before traveling to Moscow Thursday.
