VIENNA, Austria (AP) _ Eight East German youths fled to Austria from Czechoslovakia and Hungary on Saturday in two separate pre-dawn escapes, a spokesman for the Interior Ministry said.

One group swam a reservoir, and the other reportedly scaled barbed-wire fences.

Five of the eight crossed the Hungarian border at 4 a.m. near the town of Rechnitz, said the spokesman, who demanded anonymity. They told Austrian officials they climbed over the barbed wire fences marking the border, the Austria Press Agency said.

Ten minutes later, about 180 miles away, the other three swam to Austria across the Lipno reservoir from Czechoslovakia, the spokesman said. They arrived in St. Oswald, a village in northern central Austria barely a mile from the border.

''There were no difficulties'' with the escapes, the spokesman said. ''We would certainly have noticed if the Czechoslovaks or Hungarians had shot at these people.''

Most East Germans who flee to Austria apply immediately to West German officials for permission to live in West Germany and eventually settle there, he said.

The news agency said the five East Germans who came from Hungary were young men around 20 years old who said they would settle in West Germany.