The leader of Bulgaria's Socialist party has conceded defeat after exit polls showed that her party placed second in the parliamentary election held Sunday.

Socialist party leader Kornelia Ninova congratulated former Prime Minister Boiko Borisov's GERB party for winning the election.

The Socialists, who campaigned on a platform of forging closer relations with Russia, ruled out any option of serving in a coalition government with the center-right GERB party.

Ninova says that if "GERB fails to form a government, we will try to do so."

Official returns are expected Monday.