The German city of Cologne Monday announced a ramped-up police presence, more CCTV and a fireworks-free zone at upcoming New Years Eve celebrations to avoid a repeat of last years mass sexual assaults.

Hundreds of women that night described being mugged and groped in a crowd of men of mainly Arab and north African appearance, incidents that shocked Germany and fuelled criticism of Chancellor Angela Merkel's liberal refugee policy.

Cologne police chief Juergen Mathies said 1,500 officers would be deployed on the streets of the western city this year, up from some 140 last year, when police came under fire for failing to properly respond to the chaotic events.

"This must never happen again," he said at a presentation of the city's security plan for New Year's Eve.

The city will also be stepping up its video surveillance, with hundreds more CCTV cameras and more officers wearing bodycams, Mathies said.

Much of the increased security will focus on the square between the city's iconic Dom cathedral and the train station where most of the assaults took place.

Cologne mayor Henriette Reker said access to the square this year would be tightly controlled, with no firecrackers or other pyrotechnics allowed in the safety zone.

The square will also be flooded with light as part of a video and light installation by German artist Philipp Geist that will be projected onto the Dom.

Of the roughly 1,200 criminal complaints filed about last year's New Year's Eve incidents, more than 500 were for sexual assault, Cologne police reports showed.

The majority of the perpetrators were never caught. Of the suspects who were identified, many were migrants from Morocco and Algeria.

Similar assaults were reported during end-of-year festivities in other German cities.

The ugly scenes in Cologne made global headlines and deepened concerns about how to integrate the nearly 900,000 newcomers who arrived in Germany last year.