Preliminary counts put the Social Democrat CSSD party on 20.5 percent, Action for Alienated Citizens (ANO: Czech for "yes") won 18.7, and the Communist Party of Bohemia and Moravia (KSCM) lagged behind with 15 percent.

Likely new premier Bohuslav Sobotka had hinted before the polls closed on Saturday that he could form a minority government with the tacit support of the Communists.

But their third placing behind the second-placed ANO has cast doubts on that scenario.

"The result may not be what we imagined but it's the highest score of all parties," 42-year-old Social Democrat leader Sobotka told reporters in Prague.

He declared himself "ready to start talks" on a coalition with all parties in parliament.

The election ends seven years of scandal-tainted right-wing rule. During campaigning, Sobotka, a former finance minister, had proposed the introduction of new taxes on banks, utilities and wealth to pay for social programs.

'Better off'

Billionaire Andrej Babis said his newly-formed ANO would not back any deal with the Social Democrats and would prefer to stay in opposition.

"We'll be terribly glad to prevent the rise of left-wingers backed by Communists," said the 59-year-old, himself a former Communist.

The Slovak-born Babis reinvented US President Barack Obama's "Yes We Can" campaign slogan, promising Czechs "Yes, We'll Be Better Off".

Babis claimed his billions made him immune to bribery and had wooed voters with vows of squeaky clean politics.

Prediction

Jan Outly, an analyst at Prague's Metropolitan University said the "most likely coalition" could comprise Sobotka's Social Democrats, the right-wing Christian Democrats, with backing from ANO.

Together the three parties could control 111 seats in the 200-seat parliament.

An elective backlash

Right-wing Prime Minister Petr Necas gave up his post in June amid an affair over surveillance and bribery.

His Civil Democrats (ODS9 drew only 7.7 percent on Saturday. The allied right-wing Top 09 of former foreign minister Karel Schwarzenberg garnered 12 percent.

Both parties will remain in parliament.

Swing began in January

Voters had already swung left in January, electing former Communist Milos Zeman as president after a decade under the right-wing euroskeptic Vaclav Klaus.

Polls opened Friday afternoon and closed 24 hours later on Saturday. Unlike other EU countries, predictions via exit polls were not expected. The 200 seats in the Chamber of Deputies, the lower house, were contested by nearly 5,900 candidates. Voter turnout topped 59 percent.

The Czech Republic, home to 10.5 million people and an EU member, has existed since its 1993 Velvet Divorce from Slovakia. That followed the collapse of communism and four decades of totalitarian rule in the former Czechoslovakia, which ended in 1989's Velvet Revolution.

mkg/rc, ipj (Reuters, AFP, dpa)