Polish President Bronislaw Komorowski has vowed to urgently seek a referendum on voting and tax rules if he is re-elected, the day after an opposition candidate forced him into a runoff.

Nationalist party candidate Andrzej Duda is expected to receive 34.5 percent of the first-round vote, to Komorowski's 33.1 percent, according to the IPSOS exit poll released by the private TVN24 and the state-run PAP news agency following Sunday's vote. Official results could be announced late Monday, according to state electoral authorities.

In reaction to Duda's good showing, Komorowski vowed to seek urgent reforms.

On Monday he said he will call a referendum that will propose changes to voting and to tax regulations, but gave no date for it.

Komorowski's current five-year term ends in August.