Police say an Indian student in Germany has been attacked and injured by suspected Islamic extremists who accosted him and demanded that he convert to Islam.

Police spokesman Frank Piontek said on Thursday that two attackers in the western German city of Bonn severely beat the 24-year-old and then slashed his tongue with a knife.

Police say the attackers walked up to the student in a city street late Monday and demanded that he convert to Islam then beat him up after he refused to do so.

The student, whose identity wasn't given in line with German privacy rules, was taken to a hospital for treatment. He was released a day later.

The Bonn police's department for politically motivated crimes is investigating.