Adding fresh dirt to his mud-slinging match with Mikhail Gorbachev, President Boris Yeltsin released documents that appeared to link the former Soviet president to a cover-up of the Katyn massacre of Polish officers in World War II.


A Yeltsin spokesman Wednesday displayed some top secret Communist Party documents that catalogue a half century of efforts to cover up the fact that Soviet troops in 1940 executed some 25, 000 Polish officers around the Katyn forest, near Smolensk.


"The respected Mikhail Sergeyevich long ago - many years ago - knew of this tragedy and the true identity of the guilty ones", Vyacheslav Kostikov told reporters at a Kremlin briefing, according to Reuters. "But he remained silent".


It was Gorbachev who gave the order to reveal the truth about the Katyn massacre in April 1990. But Kostikov said one of the files released showed that Gorbachev was given documents on the massacre in April 1989, meaning that he had known the truth for at least a year.


Yeltsin and Gorbachev have been antagonists for several years, and the fight has intensified in recent weeks over Gorbachev's refusal to testify at a Constitutional Court trial on the legality of the Communist Party, which he led from 1985-91. When Gorbachev first declined to testify, before the trial opened this summer, Yeltsin's press and information minister, Mikhail Poltoranin, threatened to release a series of documents "of the most scandalous sort" bearing his signature.


But the latest attack came only one day after there appeared to have been some rapprochement between the two men,


On Tuesday, the Russian authorities lifted a travel ban on Gorbachev so that he could attend the funeral of Germany's former chancellor, Willy Brandt, while Gorbachev offered to appear at a closed session of the Constitutional Court.


Gorbachev's refusal to testify at the trial prompted the original travel ban, which was imposed Oct. 2.


By Wednesday, any signs of goodwill had gone, as the court refused Gorbachev's compromise offer and Gorbachev was forced to cancel a trip to Milan in Italy. The travel restriction has apparently been lifted only for Gorbachev's visit to Germany on "humanitarian grounds", and the Russian Foreign Ministry said that his passport had been stamped only for Germany.


"I apologize to all my Italian friends", Reuters quoted Gorbachev


as telling Italian state radio. "It's not my fault - my passport only allows me to go to Germany".


Flatly refusing Gorbachev's offer Wednesday, Valery Zorkin, the court's chairman, said, "Why does he aspire to a private conversation and cannot appear at the hearings? Why is he trying to be a judge of the court? No individual citizen has the right to dictate conditions to the court".


Karen Karagezyan, a spokesman for the former Soviet president's research institute, the Gorbachev Foundation, said that Gorbachev had originally been told that the court's decision would allow him to go to Italy.


But when Gorbachev turned to Russian authorities for clarification, he was told the trip had been banned for "unknown, unclear reasons", according to a foundation statement.