Poles have started voting in the final round of a cliffhanger presidential election with incumbent Bronislaw Komorowski trying to fend off the challenge of conservative newcomer Andrzej Duda.

After nearly eight years in power, the centrist Civic Platform (PO) - associated with Komorowski - is running neck and neck in the polls with Duda's right-wing opposition Law and Justice Party (PiS).

Komorowski, a 62-year-old communist-era dissident, has been popular and was easily expected to win re-election on May 10, but was stunned by his razor-thin defeat in the first round to his challenger.

Neither candidate however received the 50 percent of votes needed to win the election outright.

Duda, a 43-year-old lawyer and and member of the European Parliament with the Law and Justice party, scored a victory by just one percent by winning over disillusioned voters with promises of generous social spending, an earlier retirement age and lower taxes.

Polls in recent days have shown Sunday's race as being too close to call. The first round had a large protest vote for a rock star.

"The victory of one or the other will be a narrow one and is impossible to predict on the basis of polls," Stanislaw Mocek, a political scientist at the Polish Academy of Sciences, told the AFP news agency.

Exit polls will be published when polling stations close at 9pm local time (19:00 GMT), but final results are not expected until Monday at the earliest.

Source: Agencies