With 95% of votes counted, Mr. Komorowski got 52.6%, which his rival Jaroslaw Kaczynski had 47.4%.

Mr Kaczynski had initially accepted defeat based on an exit poll, but Mr Komorowski's camp remained cautious.

Mr Kaczynski is the twin of former President Lech Kaczynski, who died in a plane crash with 95 others in April.

This run-off election was held after neither candidate gained more than 50% in the first round in June.

Poland's electoral commission says final results will not be announced until Monday afternoon.

Mr Komorowski is from the ruling Civic Platform party, while Mr Kaczynski represents the main opposition Law and Justice Party.

The election has been dominated by a catastrophic plane crash. Poland's president Kaczynski and his wife - along with other leading political and military figures - died when their plane came down in Smolensk on April 10 as they flew to attend a memorial ceremony for the World War II Katyn massacre.