Cologne police chief Wolfgang Albers has been relieved of his duties following criticism of his handling of violent clashes in the city on New Year's Eve.

Wolfgang Albers, 60, was put into "temporary retirement", said Ralf Jaeger, interior minister for the North Rhine-Westphalia state.

"My decision is necessary in order to regain public confidence in the Cologne police force's ability to act, particularly in view of upcoming major events," said Mr Jaeger in a statement, ahead of Carnival celebrations next month.

Police have said that roughly a thousand men mugged, threatened and assaulted women in the city centre on New Year's Eve.

The incident has raised pressure on local police, the state government and German Chancellor Angela Merkel.

Earlier, the German government said asylum seekers were among those involved in the violence.

A spokesperson said of the 31 suspects whose names are known "18 have asylum seeker status". 

He added that federal police had recorded several complaints about sexual offences, but "the perpetrators for these have not been identified".

The suspects include nine Algerians, eight Moroccans, four Syrians, five Iranians, one each from Iraq, Serbia and the United States, and two Germans, he said.

Cologne's state police have separately confirmed recording some 121 complaints of assaults, ranging from two alleged rapes to several accounts of groping, in what were apparently coordinated attacks in a large crowd of revellers during year-end festivities.

Victims blamed men of "Arab or North African" appearance, inflaming a heated public debate about Germany's ability to integrate the nearly 1.1 million asylum seekers the country took in last year.

Meanwhile, Slovak Prime Minister Robert Fico has called for an extraordinary EU summit following the attacks.

"I'm surprised to see the leaders of the opposition continue to trivialise - even after the attacks in Cologne and other European cities - the security risks associated with unregulated and uncontrolled migration within the EU," Mr Fico said.

"I call on the president of the European Council, Donald Tusk, and the president of the European Commission, Jean-Claude Juncker, to look into accelerating the decision on putting in place a European coastguard and border guard corps.

"For that reason it will be necessary to also convene an extraordinary summit," he said.