A German folk festival descended into violence after Iraqi and Afghan asylum seekers were accused of sexually harassing local women, it has been reported.

Several cases of sexual harassment and aggression were reported at Volksfest in the town of Schorndorf, Baden-Wuerttemberg state, police said.

No arrests have been made but police are treating a 20-year-old Iraqi man as a suspect - and three Afghan asylum seekers in a separate incident in which a 17-year-old girl was groped.

A crowd of more than 1,000 are reported to have hurled bottles at police officers who moved in to detain one of the suspects on charges of dangerous physical assault.

A German folk festival in the town of Schorndorf, Baden-Wuerttemberg state, descended into violence after Iraqi and Afghani asylum seekers were accused of sexually harassing local women (file photo of Oktoberfest in Munich)

Police said small groups of youths, many of whom are said to be immigrants, then began to vandalise the town which is home to just 40,000 people.

Authorities claimed they were roving through the streets armed with knives and replica handguns, firing flares and teargas.

Several police cars were sprayed with graffiti in the small town also dubbed 'Daimler city' because automotive inventor Gottlieb Daimler was born there in 1834.

The violence escalated when one of the suspects resisted arrest

Police chief Roland Eisele urged any women who were abused over the weekend to come forward.

He said 'the aggression and escalation of violence' was unprecedented in the town, near Stuttgart, and that the local police force had to request backup from other cities.

Police chief Roland Eisele (right, with mayor Matthias Klopfer) urged any women who were abused over the weekend to come forward

Police said in a statement that many youths 'with migrant backgrounds' were seen in the crowd, but Eisele said that it was impossible to estimate a percentage.

In a press conference Monday, Eisele evoked the chaos of Cologne's infamous 2015 New Year's Eve celebrations when men of North African and Middle Eastern appearance groped and assaulted hundreds of women, sparking widespread public outrage.

He stressed that the rowdy scenes in Schorndorf were less intense than those in Cologne or, more recently, the G20 riots in the northern port-city of Hamburg.

Far-left and anarchist militants burnt street barricades and threw rocks from rooftops during the meeting of world leaders.