Poland's populist ruling party set to lose its majority, exit poll shows

Poland's populist ruling party appeared to be on the brink of losing power, after an exit poll in a bitter and high-stakes national election predicted that the country's opposition has the clearest path to forming its next government.

The poll projected that the Law and Justice party, known by its Polish acronym PiS, would win the most seats after Sunday's vote.

But it would fall some way short of a parliamentary majority, and the opposition bloc - led by former Polish prime minister and European Council president Donald Tusk - appeared on course to gain control if it struck deals with smaller parties.

Both Tusk and Jaroslaw Kaczynski, the PiS chairman and Poland's de facto leader, attempted to declare victory on Sunday night. In reality, however, days of negotiations may lie ahead until the make-up of the country's new government becomes clear.

"The exit poll results give us the fourth victory in the history of our party in the parliamentary elections and the third victory in a row; this is a great success of our formation and our project for Poland," Kaczynski told supporters.

But in an admission of the tall order facing his party, he added: "We still face the question of whether this success will be able to be transformed into another term of office of our government. And we don't know that yet. But we must have hope and we must also know that regardless of whether we are in power or in the opposition, we will implement this project in various ways and we will not allow Poland to be betrayed."

Tusk appeared buoyant, saying: "This is the end of bad times, this is the end of the rule of PiS." He said his group's supporters "have won freedom, we have won our Poland back."