* WikiLeaks says moving to servers in Europe

* U.S. Senator says has more questions for Amazon (Recasts; adds WikiLeaks and expert’s comments)

WASHINGTON, Dec 1 (Reuters) - Amazon.com Inc AMZN.O has stopped hosting WikiLeaks' website after an inquiry by the U.S. Senate Homeland Security Committee amid anger about the release of classified U.S. government documents on the site.

WikiLeaks turned to Amazon to keep its site available after hackers tried to flood it and thus prevent users from accessing the classified information posted. WikiLeaks said on Wednesday it was now being hosted by servers in Europe.

Staff for Senate Homeland Security Committee Chairman Joe Lieberman had questioned Amazon about its relationship with WikiLeaks on Tuesday and called on other companies that provide web-hosting services to boycott WikiLeaks.

“I wish that Amazon had taken this action earlier based on WikiLeaks’ previous publication of classified material,” Lieberman, an independent, said in a statement. “I call on any other company or organization that is hosting WikiLeaks to immediately terminate its relationship with them.”

WikiLeaks has said since Sunday, when the first of its latest cache of U.S. government documents were published by media outlets, that its site was the target of a “distributed denial of service” attack, which is a computer attack meant to overwhelm a website and render it unavailable.

A representative for Amazon, which is widely known for its Internet retail business but also offers smaller Internet-hosting services, did not respond to requests for comment.

WikiLeaks slammed Amazon for dropping it, saying via the social media network Twitter that if Amazon was “so uncomfortable with the First Amendment (of the U.S. Constitution), they should get out of the business of selling books.”

WikiLeaks obtained scores of internal U.S. State Department communications, some of which were classified and included candid and embarrassing assessments of world leaders, and released them via media outlets and its own website.

Earlier this year, the website also released thousands of U.S. classified documents related to the wars in Iraq and Afghanistan, drawing condemnations that the information could endanger U.S. forces and those helping the war efforts there.

The U.S. Justice Department and Defense Department are investigating how the treasure trove of documents wound up in WikiLeaks hands. The prime suspect has been a former U.S. Army intelligence analyst, Bradley Manning.

Even though Amazon has stopped providing the web-hosting services to WikiLeaks, Lieberman suggested that his problem with the company was not fully resolved.

“I will be asking Amazon about the extent of its relationship with Wikileaks and what it and other web service providers will do in the future to ensure that their services are not used to distribute stolen, classified information,” Lieberman said.

Ryan Calo, a lecturer at Stanford University’s Center for Internet and Society, said that under U.S. law, Amazon would likely have been shielded from any possible prosecution by the government over the WikiLeaks document dump.

“It would set a dangerous precedent were companies like Amazon to take down things merely because the senator or another government entity started to ask question about them,” Calo said. (Additional reporting by Alexandria Sage in San Francisco, Alex Dobuzinskis in Los Angeles and Tim Castle in London; Editing by Doina Chiacu and Cynthia Osterman)