My telephone won't start working after a failed update

Hallo, I have an iphone 5 and today there was an update which occured on my laptop, while I was charging my phone with its USB. Itunes automatically opened as always, I allowed the update but something went wrong and it did not work out, so now my phone won't start working. On the display of my phone there is a black screen with only an Itunes icon and a picture of the USB cable, pointing to the Itunes icon. I tried to restart it but after switching off, the same thing occurs on the display. What could be wrong with it?