"Technical investigations are ongoing due to abnormal attempts to access the site," Vatican spokesman Matteo Bruni said, without giving any further information.
The suspected hack came a day after Moscow criticised Pope Francis's latest condemnation of Russia's invasion of Ukraine.
In an interview with a Jesuit magazine, the pope had singled out troops from Chechnya and other ethnic minorities in Russia for their particular "cruelty" during the war.
(Reporting by Crispian Balmer; Editing by Gareth Jones)
