A few times a day, an elderly Czech person will pay a visit to the photography exhibition in Prague’s Old Town Hall, which chronicles the crushing of the Prague Spring by Moscow in 1968, and complain as they leave.

“‘The Russians are here again,’ they grumble to me,” said the curator, Dana Kyndrová, describing locals’ views on the thousands of Russian tourists who visit Prague each week and the 30,000 Russians who have residency permits in the Czech Republic.

Tuesday marks the 50th anniversary of Moscow sending half a million troops from the Soviet Union and Warsaw Pact countries to crush the reformist government in Czechoslovakia led by Alexander Dubček, which had been attempting to implement “socialism with a human face”.

A debate is raging about whether Russia poses a strategic threat to the country today or whether relations should be improved with Moscow in spite of EU sanctions.

Most politicians in both the Czech Republic and Slovakia see Russia as a threat, but the Czech president, Miloš Zeman, is an outspoken admirer of Vladimir Putin, while Slovakia was one of a handful of EU countries not to expel any Russian diplomats in response to the poisoning of Sergei Skripal in Salisbury in March, after disagreement among the ruling coalition.

For some of the older generation, the anger at the Soviet Union from 1968 carries over on to modern Russia and Russians. Kamila Moučková, a television newscaster who was arrested during a live broadcast in August 1968, has said in interviews with the Czech media that even now she finds it hard to be civil towards Russians.

A sign at Andel metro station – formerly Moscow station – in Prague. Photograph: Martin Divisek/EPA

Moučková was one of the first Czechoslovakian news anchors and became known for her critical broadcasts in 1968. She was later fired by the broadcaster and went to work in a plastic bag factory, returning to the screen only after the Velvet Revolution in 1989.

“After everything the Russians did here, I am not interested in getting to know that country,” she said. “Perhaps I am too old ... to change my view. Until this day, when we play hockey with Russia I do not view it as a sport but as a political matter. I even have to persuade myself internally to behave politely to Russians when they stop me on a street to ask for directions.”

After the Velvet Revolution, when Czechoslovakia finally made the transition out of communism, there was a tendency to look at the Prague Spring as merely a spat between different groups of communists. But many of the photographs on display at Kyndrová’s exhibition show how much of a national element there was in the protests.

There were signs and graffiti demanding “Russians go home”, and on the Bratislava war memorial someone had drawn a logo equating the Soviet star with the swastika.

Kyndrová was 13 at the time; her mother was a photographer who took some of the photographs on display. “My father took me out on to the streets and said: ‘Look at this and remember it forever.’”

Later she studied foreign languages, learning French and Russian – much to the irritation of her grandfather, who after 1968 did not want anyone in the family to speak Russian. She ended up travelling to Russia frequently from 1976 onwards, and has released a photography collection about Russia.

“The events of 1968 still play a part in the way I think about Russia. Russians always are very friendly when they find out you’re Czech, but it’s better not to talk about history,” she said.

In contemporary Russia there is still a denial about what Moscow’s troops did in Hungary in 1956 and Czechoslovakia in 1968, with all the focus instead on the heroics of the second world war victory. Kyndrová said she had an exhibit planned in Moscow in 2005 called “1945-1968-1989”, exploring the different episodes of Soviet military involvement in Czechoslovakia. “But at the last minute we got a phone call and they asked to rename the exhibit ‘Russian-Czech dialogue’ and take out some of the pictures. I refused.”

In Slovakia and the Czech Republic there are those on both the far left and the far right who favour improved relations with Russia and dismiss the historical grievances as irrelevant. “Think of our history with the Germans, and now we are friends,” said Jaroslav Doubrava, 70, a senator and one of the most enthusiastic supporters of modern Russia among Czech politicians.

Doubrava had recently returned from a trip to Crimea, organised despite heated protests from the Ukrainian embassy in Prague. He praised Russia for “performing miracles” in the territory.

Peter Marček, an independent Slovak MP who had recently made a separate trip to Crimea, said: “To me, August 1968 was the aggression of the communist Soviet Union, not a hostile act of the Russian nation.”

Unlike Poland or the Baltic states, the two countries do not have a centuries-long complicated history with Russia. For many ordinary Czechs, Russia is of minimal importance. It may not be deep-seated distrust of Russia rooted in 1968 that is behind the anti-Russian political mood, but recent actions by the Kremlin.

“During the Velvet Revolution there was almost a total absence of anti-Russian rhetoric. When [Václav] Havel was elected we went to Washington first and went straight to Moscow and met with [Mikhail] Gorbachev,” said Michael Žantovský, a former Czech ambassador to Britain and the US and an adviser to Havel, the dissident writer who became president in 1989.

“Havel had a good relationship with both Gorbachev and [Boris] Yeltsin, but distrusted Putin from the beginning. It was only after the invasion of Crimea that the largest part of Czech politicians condemned Russia,” he said.