Czechoslovakia announced today what amounts to a blanket amnesty for some 75,000 citizens who fled the country after the 1968 Soviet-led Warsaw Pact invasion.

The official CTK news agency announced that the government recently approved a measure allowing emigres to normalize their positions retrospectively.

Observers said that with their position abroad regularized, they would presumably be able to return on foreign passports without being treated as dual nationals and being subject to arrest and prosecution for leaving the country illegally.

Hungary took similar action several years ago. Many of the thousands of Hungarians who fled the country at the time of the 1956 uprising now visit Hungary as citizens of their new countries and Hungarian authorities have scrupulously adhered to the government's pledge to honor their new citizenships.

Czechoslovakia presumably timed the amnesty announcement to coincide with the preparatory talks at the Belgrade conference, which is to review compliance with the 1975 Helsinki agreement on security and cooperation in Europe. Free movement of people across national borders was one of the pledges made by the 33 European nations, the United States and Canada in the Helsinki accord.

While allowing those who fled Czechoslovakia in 1968 to normalize their departures, however, Czechoslovak authorities continue to deal harshly with many of the leading figures of the 1980 movement who remain in Czechoslovakia.

CTK said those who had been away for more than five years would now be able to apply for retroactive emigration permits or to renounce their Czechoslovak citizenship.

The agency said any who wished to do so could return home. Although it did not specify whether they would be subject to any sanctions, it was assumed that they would not.

CTK said emigres who had made unfriendly speeches against the country on television or in the press, or had harmed the country in any other way, would be deprived of their citizenship.

Those who fled abroad after the 1968 invasion were sentenced in their absence to prison terms ranging from six months to five years on charges of leaving the country illegally.

"The Czechoslovak government was led to this step by the fact that the majority of Czechoslovak citizens living abroad without the consent of the Czechoslovak authorities have expressed constant interest in contact with their country. Also, the majority of their relatives living in Czechoslovakia would like them either to return home, or to be able to meet them," the statement said.

"But despite this decision the Czechoslovak government considers illegal emigration as a negative phenomenon," the statement added.