The Indian student was attacked on Christmas eve when he was on the way to his place in Bonn.
The men enquired about his religion and asked him to convert to Islam, warning him that they would cut his tongue if he refused to do so, Der Spiegel reported.
The student, who was not identified, told the police that he was attacked by two men from behind after he ignored them.
The attackers beat him up and slashed his tongue and flew in a car.
Police spokesman did not give details of injuries but said the information that the victim gave was credible.
A passerby found the bleeding student on the road and called an ambulance. The student was admitted to a local hospital and was released a day later.
