Wikipedia has been temporarily taken offline in several countries after the website was hit with a "malicious attack".
The Wikimedia Foundation, which operates the user-edited online encyclopedia, said the site had been taken offline for "intermittent periods" in some areas.
An outage map on Saturday morning showed several European countries impacted, including the Netherlands, Germany and Poland.
In a statement, Wikimedia said the attack was ongoing and engineering teams were working to deal with the issues.
They said: "We condemn these sorts of attacks.
"They’re not just about taking Wikipedia offline. Takedown attacks threaten everyone’s fundamental rights to freely access and share information."
The organisation added: "We in the Wikimedia movement and Foundation are committed to protecting these rights for everyone."
Takedown attacks usually take the form of a DDoS - or distributed denial of service - in which a website is maliciously flooded with traffic in a bid to overload it.
Wikipedia is one of the world's most popular websites, with traffic monitoring service Alexa ranking it the 10th busiest site on the internet.
