Prague (AFP) - Thousands of Czechs protested across the EU country on Tuesday against the communist party as it was poised to play a role in government, albeit an informal one, for the first time since communism fell in 1989.

The communists are expected to throw their tacit support behind populist billionaire Andrej Babis, due to be appointed as prime minister on Wednesday for a second time after failing to win a confidence vote in parliament in January.

With 78 seats in the 200-member parliament, Babis's ANO (YES) party is expected to formally partner with the 15-seat CSSD coalition and rely on the 15-seat KSCM communists to make up the rest.

"I read a lot about the communist era and I oppose communists returning," high school student Jana Homolkova told AFP on the sidelines of a rally organised by in the heart of Prague by the "Million moments for democracy" NGO.

Protesters noted that President Milos Zeman, a former communist who makes no secret of his pro-Russia and pro-China views, is due to tap Babis, also an ex-communist, but one who went on to amass a fortune as a food, chemicals and media tycoon.

"Tomorrow will be a tragic day for Czech democracy," said Jiri Pospisil, the leader of the rightwing party TOP 09 party in front of some 10,000 protesters in Prague, according to an estimate by AFP.

"Zeman and Babis, this country isn't yours!", "Stop the communist criminal ideology!", "No more communism!", were just some of the posters touted by protesters in Prague.

They also waved portraits of the estimated 4,500 victims of the former totalitarian regime before 1989.

Similar rallies were also held in no less than 200 Czech towns and villages.

Babis's ANO (YES) won last October's general election campaigning on an anti-corruption ticket, but potential coalitions partners snubbed him over criminal charges for alleged EU subsidy fraud which he has flatly denied.

Babis has been governing as a caretaker prime minister since the failed confidence vote in January.

The KSCM communist party has signalled it will back him in a confidence vote this time around in exchange for positions in large state-owned enterprises.

It will thus have a key role, albeit informally, in forming the government for the first time since the 1989 Velvet Revolution led by Vaclav Havel that peacefully swept away communism in then Czechoslovakia.