Voters are choosing from among 11 candidates, with the outcome uncertain.
Facing a slump in popularity, the AfD is seeking to enter national parliament for the first time.
The Pope also laments that "international accords are more important than human rights".
BBC correspondent recalls interview with murdered Paris officer
Why Rome is sending trains full of rubbish abroad
Will tennis star Sharapova still be a big hit with sponsors?
Squeeze on university likened to Russian tactics
The gay man fleeing torture in Chechnya
Dortmund bombing linked to financial scam
Broadcast time 11:06 BST - 11:30 BST
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Broadcast time 21:06 BST - 22:00 BST
Will and Kate on their new mental health campaign