Police say a group of Pakistanis and a Syrian have been attacked in Cologne amid tensions over New Year's Eve assaults in the city that have been blamed largely on foreigners.

They say six Pakistani nationals were attacked Sunday by a group of around 20 people and two of them were briefly admitted to a hospital. Also on Sunday evening, a Syrian man was attacked by five people. He was injured but didn't need treatment.

Police say they are still investigating whether the attacks were racially motivated and whether there was any link to the New Year assaults. Those assaults have stoked tensions over Germany's open-door policy in the refugee crisis and prompted politicians to call for tougher laws against migrants who commit crimes.