Opinion polls ahead of the election gave the lead to the Social Democrats (CSSD) but the left-wing party seemed likely to fall short of a stable majority.
Survey indicated the CSSD would win 26 per cent, with 18 per cent voting for the Communists and 16.5 per cent for the populist party ANO formed by billionaire Andrej Babis.
Tipped as the next premier, Social Democrat leader Bohuslav Sobotka has said his party could go it alone in a minority government, relying on the tacit support of the Communists.
Voters already veered left in January, electing ex-Communist Milos Zeman president after a decade under the right-wing and eurosceptic Vaclav Klaus.
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Babis, a Slovak-born farming tycoon and media mogul, has capitalised on the discontent with the right with a populist campaign vowing squeaky-clean politics.
"If they can't agree (a coalition government), the powerful president could propose a government or call fresh elections," the top selling Dnes broadsheet warned today.
Coalition governments lacking comfortable majorities are the norm on the fragmented Czech political scene. Smaller parties or independent MPs are often wooed for support.