Prague - Czechs and Slovaks on Thursday commemorated 40 years since Soviet tanks crushed the Prague Spring communist reform movement, which threatened Moscow's Cold War grip on eastern Europe.

Warsaw Pact troops invaded what was then Czechoslavkia in the early hours of August 21, 1968, taking control of the country and arresting the reformist leaders. Western nations denounced the crackdown but made no military move to stop it.

In the run-up to the emotional anniversary, Czech leaders and European commentators have drawn comparisons between 1968 and Russia's invasion of Georgia. So did US Secretary of State Condoleezza Rice.

"The Russian tanks on the streets of Georgian towns remind those of us who experienced it of the 1968 invasion," Czech Prime Minister Mirek Topolanek said in a recent newspaper article.

At an anniversary event in neighbouring Austria, Foreign Minister Ursula Plassnik lashed out at Russia for its assault on Georgia.

"A power of the future cannot rely primarily on tanks for its foreign policy," she said in Vienna. "We never want to have to fear Russia again."

German Chancellor Angela Merkel, who grew up in her country's formerly communist east, has urged people not to forget the "brutal crushing" of the Prague Spring.

On Thursday, Czech and Slovak government leaders - the two parts of the country split peacefully in 1993 - planned to mark the anniversary at events in both capitals, Prague and Bratislava.

Prague's National Museum was opening an exhibit with mementos and recollections from ordinary citizens. An old Soviet tank was parked outside the building as part of the show.

Also in the show are stories and personal items from Jan Palach, a Prague student who set himself on fire in January 1969 to protest the invasion. He died a few days later, making him a martyr of the fight against communism.

However, a recent poll found that 70 per cent of Czechs younger than 20 have "no opinion" on the events of 1968.

Among Prague's expected guests were former dissidents from Russia, Bulgaria, Poland, Hungary and East Germany who protested the invasion in their home countries.

One of them, Natalya Gorbanevskaya, now 72, was among eight Russians who demonstrated in Moscow's Red Square on August 25, 1968. She was punished with internment in a psychiatric hospital.

Czechoslovakia's ferment began in early 1968 as a new generation of Communist leaders led by party chief Alexander Dubcek pushed to reform a declining economy and loosen the party's choking grip on civil life. It was dubbed socialism "with a human face."

The Warsaw Pact invasion shocked the West but, in keeping with Cold War logic, there was no military response.

Afterwards, the Soviets installed a loyal regime that purged the reformists over the next few years.

It took another two decades before communism fell and democracy came to Czechoslovakia in the 1989 Velvet Revolution. The last Soviet soldier left in 1991 and Dubcek lived to see the overthrow of communism, dying in 1992 at age 70.

In a 2006 visit to the Czech capital, then-president Vladimir Putin expressed Russia's "moral responsibility" for crushing the Prague Spring. (dpa)