The following day and for the next four days my credit card was debited for amounts just below and above 9 Euros. I initially thought the debit was for another future purchase I made at Amazon, though I was a little surprized as usually Amazon debit only when they ship the product, but I wasn't expecting to be debited 4 times.
Yesterday I contacted amazon using their chat service. After some considerable exchanges it was clear that someone had created an account at Amazon with my credit card. Amazon cancelled the purchases and have promised to refund me, but were unable to cancel the fake account as it had been created at amazon.de. I was told to contact amazon.de.
I did so again in chat mode, using my broken German, but the representative was very responsive and immediately forwarded my story to their fraud department. He managed to cancel the fake account and confirmed that the fake purchases were in the process of being refunded.
A couple of hours later I got a message from the fraud department, which invited me to block my credit card, which I immediately did. There have been no further fraudulent charges on the card.
The behaviour of the hacker was odd. He was clever in only making small purchases, which might easily have gone unnoticed. However, although registering on amazon.de, the purchases were for digital versions of English language books. Amazon refused to give any further details of the fraudster.
I found the chat contact with Amazon to be efficient and responsive, with no waiting times to be connected.