Germany plans to make it easier to deport criminal foreigners following public outrage over New Year's Eve assaults in Cologne.

Police say 553 criminal complaints have been filed in connection with the assaults, with about 45% involving allegations of sexual offences, and most of the suspects identified so far are foreign nationals.

Many asylum-seekers who commit crimes currently avoid deportation because the danger they face in their home country is considered greater than the reason for deporting them.

Interior minister Thomas de Maiziere told reporters in Berlin: "With this proposal we are significantly lowering the hurdles for the possible expulsion of foreigners who have committed crimes in Germany."

The changes, which have to be approved by the cabinet and parliament, would mean that even a suspended prison sentence would be grounds for deportation if someone is found guilty of certain crimes. These include homicide, bodily harm, sexual assault, violent theft and serial shoplifting. Youth sentences would be covered.

A sentence of more than one year would further increase the likelihood of deportation, Mr de Maiziere said.

"That's a hard but right response by the state to those who are seeking protection here, but think they can commit crimes" without consequences for their right to remain in Germany, he said.

Justice minister Heiko Maas said public pressure after the Cologne assaults played a role in getting the plan agreed so quickly.

"We owe this to the victims of these serious crimes," he said, adding that the measures were also necessary "to protect the overwhelming majority of innocent refugees in Germany. They don't deserve to be lumped together with criminal foreigners".

Mr Maas said changes would be made to Germany's sex crime laws to ensure that victims who are caught by surprise, or who fear greater physical harm if they resist assault, are better protected.

"This too is the kind of situation we had in Cologne, where people were confronted with a horde of men," he said.

Police say most of the suspects in Cologne are believed to be foreigners, including at least some asylum-seekers. Many were described as being of "Arab or North African origin".

The assaults have heightened tensions over Germany's migrant influx. Nearly 1.1 million asylum-seekers arrived last year.

Cologne police say they have identified 23 possible suspects. Separately, federal police have identified 32 suspects, including nine Algerians.

Germany is also keen to ensure that migrants who are not granted asylum leave the country as quickly as possible.

Separately on Tuesday, a senior German police official said he does not believe the New Year's Eve assaults in Cologne and elsewhere were linked to organised crime.

Holger Muench, head of the Federal Criminal Police Office, said "the same conditions were in place at different locations", with crowds of people gathering to celebrate the new year.

"I am not saying that there was no organisation, but it is not organised crime," he said. "That would have a different quality for me. We would be talking about ... hierarchical groups."

However, "what we see here is perpetrators communicating with each other and making arrangements... and of course we must recognise better where they do this, how they do this".