German Chancellor Angela Merkel's coalition government has backed a new law to make it easier to deport foreign nationals who commit crimes, in the wake of attacks on women on New Year's Eve, many blamed on migrants.

More than 600 women have complained of being attacked in Cologne and other cities. Police have said their investigations are focused on illegal migrants from north Africa as well as asylum seekers.

The proposal by Justice Minister Heiko Maas and Interior Minister Thomas de Maiziere will make it easier to deport non-EU foreign nationals found guilty of committing physical and sexual assaults. The law will not apply to citizens of the European Union.

"Nobody among us should be above the spirit and the letter of the law," Mr Maas said in a statement. "If they are criminal foreigners, in future they will be threatened with even faster deportation."

Foreigners convicted of resisting police or crimes against property will face compelling grounds for expulsion, as long as the offences were committed using violence, threats or trickery.

The law should also make it easier to deny asylum status to new arrivals who are sentenced to at least one year in prison.

Germany, which took in more than 1.1 million asylum seekers last year, has been shaken by the assaults which have deepened scepticism towards Chancellor Merkel's refugee policy.

Mr Maas said the new law should help protect the hundreds of thousand of refugees who do not have a criminal record.

"They don't deserve to be lumped together with criminals. Migrants among us must not be put under general suspicion," he said.

The draft law must now be approved by the Bundestag lower house of parliament.