Thousands more people demonstrated against far-right extremism in several German cities on Friday.

There were major rallies in Frankfurt, Saarbrücken, Herne and Gütersloh. Numerous demonstrations are also planned for the weekend.

In Saarbrücken, near the French border, around 7,000 people protested against an Alternative for Germany (AfD) party event.

The AfD, riding high in the polls in eastern Germany ahead of three state elections in September, reminds many Germans of the Nazi regime in the 1930s and 40s.

Those fears were only reinforced by the Correctiv Research Center reporting this month that a meeting in November was attended by several AfD figures and Austrian white supremacist Martin Sellner.

Repatriation of those not of German blood, and even sending naturalized German citizens back to their countries of origin or "remigration," was reportedly discussed, prompting the widespread protests.

Police said around 3,000 people participated in the "We are more" rally in Gütersloh when only 500 were expected.

A similar number was demonstrated in Herne while thousands of people also marched in Frankfurt. Placards read "No state money for fascists" or "Repatriation to your knees." According to police, the events remained peaceful.

The Interior Ministry said more than 900,000 people took part in protests in Germany last weekend.

The demonstrations have spread to Austria, birthplace of Nazi leader Adolf Hitler. The country joined Nazi Germany in a union in 1938 and has flirted with far-right politicians in recent decades.

In the capital, Vienna, about 35,000 demonstrators braved rain to gather near the parliament building on Friday evening, police said. Organizers estimated the turnout to be around 80,000 people.

"We are here to defend democracy and stand up against the extremist movements that are growing in Europe," one participant, Elena Tiefenboeck, told AFP.

"So that the past doesn't repeat itself" at a time when the far-right Freedom Party (FPOe) is expected to win this year's parliamentary elections, the 25-year-old student said.

A win by the FPOe would be a "very worrying" prospect that could further "polarise society," said 53-year-old psychotherapist Barbara Brauboeck.

One banner read "Kickl is a Nazi" about the FPOe's hardline leader Herbert Kickl, known for his fiercely anti-migrant campaigns.

"Some of us have already packed their bags or are thinking about which country to flee to," said local politician and activist Mireille Ngosso, according to public broadcaster ORF.