Exit polls suggest it has enough seats to govern alone, with an anticipated 39% of the vote.

Its eurosceptic leader Jaroslaw Kaczynski has claimed victory, and the outgoing Prime Minister, Ewa Kopacz of the centrist Civic Platform party, has admitted defeat.

Law and Justice has strong support in Poland's rural areas.

If the numbers suggested by the exit poll are confirmed, it will be the first time since democracy was restored in Poland in 1989 that a single party has won enough seats to govern alone, the BBC's Adam Easton in Warsaw says.

"We will exert law but there will be no taking of revenge. There will be no squaring of personal accounts," said Mr Kaczynski. "There will be no kicking of those who have fallen through their own fault and very rightly so."

Prime Ministerial candidate Beata Szydlo said she was grateful for the support of the Polish people:

"We have won because we have been consistent in facing all the challenges ahead of us and we followed in the footsteps of the late President Lech Kaczynski," she said.

"We wouldn't have won had it not been for the Polish people who told us about their expectations and needs, and who in the end voted for us."

-BBC