The Vatican website www.vatican.va was inaccessible. A spokesman said he could not confirm that the crash was the work of the hackers group but said technicians were working to bring it back up.
A statement on the Italian website of the loosely-knit cyber-activists group accused the Church of being responsible for a long list of misdeeds throughout history, including the selling of indulgences in the 16th century and burning heretics during the Inquisition.
“Today, Anonymous has decided to put your site under siege in response to your doctrine, liturgy and the absurd and anachronistic rules that your profit-making organization spreads around the world,” the website said.
It also accused the Vatican of being “retrograde” in its interfering in Italian domestic affairs “daily.”
Anonymous, along with another group LulzSec, has taken credit for a number of high-profile hacking actions against companies and institutions, including the CIA.
The action against the Vatican comes a day after the arrest of six suspected leaders of Anonymous by U.S. authorities.