Latest: Merkel aims "to win back" far-right voters, as exit polls show she heads for fourth term

Latest: Angela Merkel has conceded that "of course we would have preferred a better result, that's completely clear".

Update 6.32pm: Angela Merkel has conceded that "of course we would have preferred a better result, that's completely clear".

She noted that her party has been in power for 12 years and said the last four years have been "extremely challenging".