The loosely organized group of hackers known as Anonymous claimed it was targeting the ministry's website to protest Britain's treatment of Assange, who is taking refuge inside Ecuador's embassy in London to avoid extradition to Sweden for questioning over sexual misconduct.
Ecuador granted the 41-year-old Australian diplomatic asylum last week, but Britain has said it will not grant him safe passage out of the U.K., insisting that it must follow the law and deliver him to Sweden on a binding European arrest warrant.
Assange claims that if Britain extradites him to Swedish authorities, he will be handed over to the U.S. as part of a Washington-orchestrated plot to make him stand trial in the U.S. for revealing a trove of American diplomatic and military secrets. The U.S. says such claims are "wild assertions" that try to deflect attention from the sexual misconduct allegations Assange faces in Sweden.
Anonymous said on Twitter on Monday that it aimed to take down a number of British government websites as part of a campaign called "Operation Free Assange," warning "Gov. of UK expect us!"
The Justice Ministry said its website was "experiencing some disruptions" but that no data has been lost.
"This is a public information website and no sensitive data is held on it. No other Ministry of Justice systems have been affected," it said in a statement. "Measures put in place to keep the website running mean that some visitors may be unable to access the site intermittently."
The website's main home page appeared to be down late Monday, although its other content pages are functioning normally.