Poles vote on Sunday in a knife-edge presidential election that may shape the country's future relations with the European Union, already frayed by the bloc's concerns over the rule of law, EDNews.net reports citing Aljazeera.

Incumbent Andrzej Duda, an ally of the ruling nationalists Law and Justice (PiS), takes on liberal Warsaw Mayor Rafal Trzaskowski after a campaign that has shown sharply contrasting visions for the future and exposed deep political divisions.

Duda's re-election is crucial if PiS is to deepen judicial reforms that the EU says increase political control over the courts.

The president holds the power of veto and Trzaskowski has said he will block legislation that he believes would undermine democratic norms.

Given that Poland's president holds few executive powers, it is unlikely Trzaskowski could bring about significant change if he won. But if the presidency as well as the upper house of parliament were in opposition hands, PiS's ability to implement its agenda would be hampered.

The election is a runoff after a first round on June 28. Polling stations opened at 05:00 GMT and close at 19:00 GMT, at which point the results of an exit poll will be announced.

Duda has painted himself as a defender of Poland's Catholic values and the generous social benefit programmes that have transformed life for many, especially in the poorer rural regions of the EU's largest post-communist member.

"I believe we can build the Poland we dream of; a fair Poland, a rich Poland, a strong Poland... a Poland that can protect the weak and doesn't have to fear the strong," Duda told supporters on Friday, asking them to compare their standard of living now with what it was before he took office.

However, while Duda vows to stand on the side of the weak, critics say his campaign has also drawn on homophobia and anti-Semitism.

He has compared what he calls LGBT "ideology" to Soviet-era communist indoctrination, while state television has used the sensitive issue of Jewish property restitution to attack Trzaskowski.

"There are very energetic attempts, and at the centre of these attempts is Mr Trzaskowski, to see to it that in Poland different kinds of minorities can... terrorise the rest," said Jaroslaw Kaczynski, the leader of PiS and Poland's de-facto ruler.

Trzaskowski became a target for religious conservatives, who attacked him for promoting gay rights after he took part in pride marches and pledged to introduce sex education classes in Warsaw schools.