German Chancellor Angela Merkel has been re-elected for a fourth term in federal elections, exit polls suggest.

Her conservative CDU/CSU alliance has won 32.5% of the vote, remaining the largest party in Germany's parliament, according to the ARD poll.

Its coalition partner, the social democratic SPD, has gained 20%.

Meanwhile, the AfD, a nationalist, anti-Islam party, was on track to win 13.5%, emerging as Germany's third-strongest party.