Ground Personnel stated they parked the tug too close to equipment and when they backed up they hit a vehicle.

Narrative

At the arrival of the flight I parked close to the gate to help the crew with the GPU and the aircraft. When I parked at the gate was in an open area but when I returned to the tug to move to the working area a service vehicle parked too close to my equipment in a way that I couldn't move right or left; the only way of moving my tug was backing up. I backed up and I stopped when I saw that I was clear to turn around. I never noticed that I hit a vehicle behind me. After I moved to offload the plane I was explaining to an orange vest how to do some things and I heard that I was being called. A person from FAA came to me and asked me if I knew what I did wrong and I told him that I didn't. He explained to me what happened because he saw it from another gate. I explained to him that I stopped when I saw that I was clear to move and not because I felt the bump. Having service vehicle parked so close to my tug I had to back up and didn't realize that I backed up to another vehicle. After this conversation I called management and the incident was reportedIt will be very helpful if the service vehicles would have an specific area to park when they are at a gate giving any kind of service.