Amazon.com (AMZN) said its websites in Europe suffered an outage of more than 30 minutes on Sunday night.
The online retailer said the outage was due to a "hardware failure" rather than a politically motivated cyber assault.
Amazon was one of the first companies to cut ties with whistle-blowing website WikiLeaks after the site released confidential communications by U.S. diplomatic staff.
Hackers working under the name "Anonymous" have attacked companies including PayPal and MasterCard (MA) as retaliation for cutting ties with WikiLeaks.
Amazon's sites in Germany, the U.K., France and Spain were all down for more than 30 minutes until 21:45 GMT. The U.S. website was unaffected.