BUDAPEST, SEPT. 11 (MONDAY) -- Hungary, in a move reflecting the upheaval that Soviet President Mikhail Gorbachev's openness policies are causing in the Warsaw Pact, opened its border with Austria today to allow thousands of East Germans to flee to West Germany rather than return to their Communist-ruled homeland. East Germany promptly accused its East Bloc ally of acting illegally and, in a scathing statement carried by its state-run ADN news agency, charged that Hungary "has engaged in the organized smuggling of human beings." Within hours of Hungary's announcement Sunday night, the first wave of the 6,000 East Germans who have been waiting in refugee camps crossed the Austrian border in what is expected to become the greatest mass exodus of East Germans since the Berlin Wall was built 28 years ago to block their emigration. At Nickelsdorf, the main Austrian border crossing, the refugees cheered and cried as they began pouring out of Hungary when authorities there opened the border to them at midnight, the Reuter news agency reported. As the stream quickly swelled to hundreds, accommodating Hungarian border guards briefly examined their documents and waved them on. Hungarian Foreign Minister Gyula Horn said in an interview on state television that there are now "about 60,000" East Germans in Hungary -- many of them vacationing -- and "more and more are coming, and among them there is a growing number of those who do not want to return home but want to settle primarily in West Germany." West Germany, which does not recognize the division of Germany into two separate nations and automatically grants East Germans full West German citizenship, commended Hungary on its decision and prepared to receive the refugees in camps prepared for them in Bavaria. The first cars carrying East German emigres arrived at the West German border about 4 a.m., after traversing Austria. West German Foreign Minister Hans-Dietrich Genscher, in a statement released in Bonn, rejected East Germany's contention that West Germany has tried to lure its citizens and said the East Germans were leaving because of fundamental discontent with their country's system that can be corrected only by their own government. "These Germans made a personal and most certainly a difficult decision as mature citizens and without influence from outside," he said. {In Washington, a Bush administration official called the move "a strong, positive sign that Hungary "is willing to stand by the pledge of all European countries to allow freedom of emigration and travel, a pledge that many other countries have ignored." {"We welcomed what Hungary was doing in accepting the emigres," the U.S. official said. "However, it is a problem that must be resolved by the two Germanys. The heart of the problem is that East Germany has lacked a regular emigration track, and this still has not been resolved."} East German refugees in the three camps in Hungary were officially informed of the decision at 7 p.m. local time Sunday. At Zugliget in Budapest, where 600 refugees have camped for weeks, the announcement was received with cheers and clapping, followed by feverish packing. Drivers of no-frills, East German-made Wartburgs and Trabants were revving up their lawnmower-like engines by the hundreds, preparing to embark on their journey to the West. MTI, the official Hungarian news agency, said in the Sunday announcement: "Interior Minister Istvan Horvath instructed the police and border guards to let East German citizens leave Hungary with their East German travel documents. The border guards are instructed to let them leave at any border point." The exact number of those who will make use of this new gateway to the West -- Hungary said it was temporary, but no cutoff point was announced -- can only be guessed at. The three refugee camps as of Sunday held 6,000 people, but thousands more have been in daily contact with camp officials inquiring about a possible departure date. After months of high-level negotiations involving Budapest, Bonn and East Berlin toward a mutual agreement on the issue -- and recent optimistic declarations by Hungarian authorities that this appeared possible -- Hungary announced Sunday night that it had been unable to reach a compromise with East Germany and that its decision was unilateral. Under the solution outlined by Horn on television, "The GDR {East German} citizens staying in this country can leave with their own -- in other words, GDR -- passports, to a country that is willing to receive them." "This is a temporary decision," Horn continued. "This means that we have thus suspended certain paragraphs of the 1969 Hungarian-GDR bilateral treaty on tourism." That treaty committed each country to preventing citizens of the other to go to the West without approval from their own government. Horn refused to specify any time limit, but it was clear from his statement that Hungary expects the exodus to continue for days rather than hours. "I cannot set a limit on this measure," he said, "but it is certain that it is not just 24 hours." Explaining the difficulties Hungary faced in devising a solution and the pressures under which it was acting, Horn said: "This country cannot accept, as we have already underlined several times, becoming a refugee camp." Nor, he said, could it accept the solutions proposed by the two Germanys -- Bonn's suggestion that Budapest recognize West German passports it issues to the East Germans in Budapest, or East Berlin's demand that its citizens be forcibly sent home. But a solution had to be found, Horn said, because law and order were breaking down at Hungary's border with the West as a result of the East German onslaught. In recent months, an estimated 6,000 East Germans have taken advantage of Hungary's dismantling of its border fortifications last May to flee the country illegally -- but with little Hungarian opposition. Horn said that the opening of the border, originally set for last Wednesday, had been delayed at East Germany's request to give it time to attempt to persuade refugees in the Hungarian camps to return home -- a campaign that appears to have had little success. Horn appeared fully aware of the consequences Hungary's decision may have within the Warsaw Pact, especially in the more orthodox Communist states who now have been given more ammunition to claim that Budapest cannot be trusted. Hungary, along with Poland, has adopted a number of democratic reforms along the lines of those instituted in the Soviet Union by Gorbachev, but East Germany has largely held to the hard-line positions that had characterized the East Bloc since the 1950s. Last year, Hungary started giving political asylum to ethnic Hungarian citizens of Romania, and earlier this year it broke an international treaty when it suspended work on the joint Czechoslovak-Hungarian hydroelectric project on the Danube. Horn, however, expressed the hope that relations with East Germany will not deteriorate as a result of today's move. "The government of the Hungarian People's Republic cannot be held responsible for the situation," an official communique said defensively, adding that "passing judgment about the roots of the problem is not a task for the Hungarian government." But angry East German officials, through the ADN news service, charged that "the Hungarian government has chosen to illegally allow East German citizens to travel to West Germany in violation of international treaty," and acted in a way that "is a direct interference in the internal affairs" of East Germany. It said that Hungary, "under the guise of humanitarianism, has engaged in organized smuggling of human beings." West German Chancellor Helmut Kohl and Foreign Minister Genscher both referred to the humanitarian aspects of Hungary's decision, and Genscher also took the opportunity to chastise East Germany. "This is a humanitarian decision and an act of European solidarity," Kohl said in Bonn. "I am deeply thankful to the Hungarian government." Genscher, on West German television, thanked Hungary for "making a decision of humanity and a decision that means a recognition of human rights." But in a separate statement issued by the Foreign Ministry, he called on East Germany to adopt political reforms to address the problems of those who are leaving because they "have lost hope in change and self-fulfillment at home." Genscher also rejected the suggestion that people fled from East Germany mainly for economic reasons. He said lack of hope for the future and lack of opportunity for personal development were much more important factors. East German government and party officials predicted recently that East Berlin's relations with Budapest would become cooler if Hungary suspended the treaty. "There won't be a trade war, but there will be a certain souring" of ties, an East German official said. In addition, East German and Western sources said such a decision by Hungary might prompt East Berlin to sharply curb travel to Hungary, to prevent it from becoming a permanent escape route to the West. But the East Berlin leadership is considered likely to do that only grudgingly, as it would be very unpopular among the East German populace. Czechoslovakia and Hungary currently are the most popular travel and vacation destinations for East German citizens.Correspondent Robert J. McCartney in Bonn contributed to this article.