Billed as the strangest election in Poland`s 21-year post-communist history, it was called after the death of President Lech Kaczynski and much of the country`s political and military elite in a plane crash in Russia on April 10.

The two frontrunners, both Catholic conservatives espousing family values but divided on many other issues, are far ahead of the other eight candidates in opinion polls. The winner will serve a five-year term as head of state.

Kaczynski`s twin brother Jaroslaw, a combative eurosceptic, has fought an effective campaign based on calls for solidarity in a time of national disaster, but Bronislaw Komorowski of the centrist ruling party, Civic Platform (PO), looks set to win.

Komorowski is unlikely to secure the 50 percent of votes he needs to win on Sunday, however, forcing a runoff on July 4 between the top two candidates.

Polling stations are open until 8 p.m. (1800 GMT). Exit polls showing the final estimated results will be published after the voting ends.

Around 30 million Poles in a total population of 38 million are eligible to vote. Turnout in the 2005 presidential election was only about 50 percent, and only slightly better, at 54 percent, in the last parliamentary election in 2007.

Jaroslaw Kaczynski served as prime minister briefly from 2006-07, when his nationalist views, in particular his deep suspicion of Germany and Russia, put heavy strain on Poland`s relations with its neighbours and also with the EU.

By contrast, Komorowski, a father of five and scion of the old Polish aristocracy, shares Tusk`s ambition to bring Poland into the European political mainstream, a goal that includes adopting the euro as soon as is economically feasible.

Komorowski became Poland`s acting president on Lech Kaczynski`s death in his capacity as speaker of parliament.