BONN -- Thousands of jubilant East Germans began crossing into Austria and freedom early today shortly after the Hungarian government opened the border with a dramatic announcement late Sunday, declaring that all East Germans in its territory seeking to go to West Germany will be allowed to do so.

The exodus marked the end of days and weeks of bitter frustration by mainly young East Germans seeking escape from the stultifying life and depravations of their Communist homeland.

The first to cross shortly after midnight were occupants of an orange Trabant, a car with a sputtering two-stroke engine made in East Germany, which passed the frontier as Hungarian guards at Hegyeshalom, 120 miles northwest of Budapest, waved it and the following vehicles along after a quick look at the occupants' documents.

Vanguard in W. Germany

Four hours later, the vanguard reached the West German city of Passau on the Austria border.

Crying, laughing and shouting with happiness amid the sounds of honking horns, the refugees flowed through the Austrian border town of Nickelsdorf where guards waved them on.

Once inside Austria, many left their cars and danced with joy.

Some of the cars' passengers could be heard saying, "We've made it!"

A youth in one car held a banner reading: "Give Up, Erich Honecker: Are 100,000 Refugees Not Enough?"--a reference to the ailing, hard-line East German Communist leader.

One family carried its wedding linen and a pet canary.

"It's wonderful," several shouted to reporters as they crossed the border. "It's terrific!" One man, tears rolling down his cheeks, tried to speak, but overcome by emotion, he couldn't.

"It's a great feeling but also a sad one," Dieter Hoffman from Dresden told reporters at the frontier. "No matter what things were like there, it's still home."

The televised announcement of the Hungarian decision sparked the exodus by an estimated 7,000 East Germans from refugee camps in Budapest and Lake Balaton toward the Austrian border, a drive of about three hours. Some of those without cars hired taxis in Budapest to take them to the border where they then crossed on foot.

For its part, the East German government reacted angrily, denouncing the Hungarian decision as an "organized trade in humans under the guise of humanitarian considerations."

Insists Treaty Broken

The East German news agency ADN insisted that Hungary has broken a 1969 treaty obliging both states to keep each others citizens from leaving for a Western country without express permission. And it accused West Germany of being behind the move.

The Hungarian decision could prompt many more East Germans, now vacationing in Hungary, to take advantage of the open frontier, making it the largest single flight from a Communist country since the Berlin Wall went up in 1961.

A daily average of more than 1,500 East Germans crossed into West Berlin in the days immediately preceding the start of construction of the wall, which was supervised by Honecker, then a lower ranking official. In all, about 3.5 million East Germans fled to the West between the end of World War II in 1945 and 1961.

West German Chancellor Helmut Kohl warmly thanked the Hungarian Communist regime for opening the border.