German media and politicians have warned against an election-year spike in fake news after the rightwing website Breitbart claimed a mob chanting "Allahu Akbar" had set fire to a church in the city of Dortmund on New Year's Eve.

After the report by the US site was widely shared on social media, the city's police clarified that no "extraordinary or spectacular" incidents had marred the festivities.

The local newspaper, Ruhr Nachrichten, said elements of its online reporting on New Year's Eve had been distorted by Breitbart to produce "fake news, hate and propaganda".

Dortmund police on Thursday said its officers had handled 185 missions that night, sharply down from 421 the previous year. The force's leader judged the night as "rather average to quiet", in part thanks to a large police presence.

Bild, Germany's top-selling daily, also predicted trouble ahead - pointing to the fact that Breitbart's former editor Steve Bannon had been appointed as US president-elect Donald Trump's chief strategist.

It warned that Breitbart - which plans to launch German and French language sites - could seek to "aggravate the tense political climate in Germany".