Immigrant men have groped and sexually assaulted a number of women in a German city in copycat attacks of the New Year's eve sex frenzy in Cologne.

Police said the four women who filed complaints after the incidents in Essen late on Friday could be 'only the tip of the iceberg.'

Women who may have been attacked at the Essen Original city party have been offered a confidential hotline by officers to contact them.

Immigrant men have groped and sexually assaulted a number of women in a German city in copycat attacks of the New Year's eve sex frenzy in Cologne (shown in file picture)

The police presence at the festival was beefed up over the weekend as a result of the sexual assaults.

All said that men came up to them in groups, danced around them, harassed and groped them.

This mirrored the attacks in Cologne on December 31 when mobs of North African migrants assaulted hundreds of women in attacks which served to turn Germany against the open-door refugee policy of Chancellor Angela Merkel.

Despite defending her record in a long interview on Saturday with the BILD newspaper, the chancellor is braced for a beating at the hustings on Sunday when the anti-immigration Alternative for Germany (AfD) party is set to defeat her own CDU conservatives in a regional election in her home state.

Attacks in Cologne served to turn Germany against the open-door refugee policy of Chancellor Angela Merkel

Police said the Essen victims were attacked in three parts of the city by North African men in groups of four and six 'who drove their victims into corners and groped them all over.'

Most of the abusers are still being hunted but police apprehended several lone suspects shortly after the complaints were made. Two 16-year-olds and a 46-year-old man were questioned but later released.

Police spokesman Peter Elke said: 'The heavy police presence on the ground meant we could promptly identify and arrest some suspected attackers.' All suspects are immigrants or of a migrant background.

Elke added: 'The sequence of events has to be determined. Therefore we are looking for witnesses to the attacks as enquiries continue.'

The festival continued on Sunday and will end on Monday night.

Organisers have promised to work with police to provide greater security for women in the hours of darkness when bands play and people stroll among food stands, acrobats and street artists.

The chancellor is braced for a beating at the hustings on Sunday when the anti-immigration Alternative for Germany (AfD) party is set to defeat her own CDU conservatives in a regional election. Pictured is AfD party leader Frauke Petry

The news could not have come at a worse time for the chancellor as the AfD is set to score a bigger percentage of the vote in her home state of Mecklenburg-Vorpommern on Sunday.