An exit poll by TNS OBOP for national TV indicates that Mr Tusk's party won 39.6 percent of votes, comfortably ahead of the Law and Justice party - which gained 30.1 percent - but short of an absolute majority.

Opposition leader Jaroslaw Kaczynski has admitted defeat.

Civic Platform is the first Polish party to win two consecutive terms since the fall of communism in 1989.

The official results from Sunday's election are due to be published on October 10.

Mr Tusk said he would work on forming a governing coalition on October 10. He is expected to renew his alliance with his current partner, the Peasants' Party, which has said it willing to team up with the Civic Platform again if an offer was made.