According to a police statement, the crash occurred at 6.20pm on Sunday between four Mercedes Benz Omnibuses at the Harburg bus station in the south of the city, after two buses arriving from opposite directions collided.
One bus, containing several passengers, was entering the station and presumably missed a signal to stop, causing it to crash into a second bus which was leaving the station.
The impact of the collision was so strong that one of the buses rammed into a third bus which was parked on the left hand side of the street, which then pushed a fourth nearby bus forward.
The passengers on the first bus were thrown from their seats by the impact and 15 people sustained injuries.
40 firefighters arrived at the scene shortly after to deal with the situation.
All four bus drivers and 11 passengers, including two six-year-old children, were injured in the incident.
A 47-year-old passenger was severely injured and had to be kept in hospital, but the remaining 10 passengers only sustained minor injuries and were able to leave the hospital shortly after being taken to outpatient care.
All four buses were badly damaged and are not considered driveable.