Thousands of Germans have flooded the streets to protest against major electoral gains made by the far-right Alternative for Germany party, AfD.
Exit polls show the AfD has become the radical nationalist party to enter parliament since World War II.
In central Berlin, hundreds of anti-fascist protesters surrounded the club where the AfD were celebrating their win, shouting “all of Berlin hates the AfD” and “Nazis raus” or “Nazis out.” Police blocked the club's entrance and made a handful of arrests over “small incidents,” according to authorities.
Exit polls show the AfD have won about 13.5 percent of the vote, guaranteeing them around 90 seats in the Bundestag – a surprise result for a far-right party frequently accused of harboring Nazi revivalist ambitions.
Smaller protests were held in other German cities, including Cologne in the west, where around 400 people gathered, and in the northern port city of Hamburg, where demonstrators marched towards the party's local headquarters.
While exit polls show that incumbent Chancellor Angela Merkel's Christian Democratic Union party was the election's big winner with 32.5 percent support, AfD's success has upended the post-unification status quo and shown the strength of Europe's far right.
Leading AfD candidate Alexander Gauland vowed his party would "hunt" the new government, whatever its make-up, adding: "We'll get our country and our people back."
During the election campaign, the party's leading candidates said that Germans should show pride in its war veterans — including those who fought for Adolf Hitler's Third Reich — and claimed that terror is grounded in the Muslim religion.
In France, far-right leader Marine Le Pen congratulated the AfD, tweeting: "Bravo to our AfD allies for this historic showing!"