Administrators at the popular online forum Reddit have been accused of censorship after quarantining a subreddit titled 'european.'

Subreddits, which are also known as communities, are forums dedicated to specific topics.

“The administration has decided to censor free speech for Europeans and they quarantined the subreddit on the 12th of May 2016,” says a note on the subreddit link. With the subreddit set to private, the note adds that “You must be a moderator or approved submitter to visit.” Visitors to the subreddit were also urged to continue their discussions on Voat, another online forum.

The question of bias in social media has erupted recently. The Reddit accusation came just days after anonymous allegations that contractors at Facebook deliberately suppressed conservative news on the site’s Trending Topics section. Facebook has denied any political bias, saying there is “no evidence” of the alleged activity.

Related: Zuckerberg denies Facebook has anti-conservative bias



Reddit told FoxNews.com that the 'european' subreddit violated the forum's content policy. "Quarantines on Reddit are rare - there are thousands of vibrant conversations flourishing on the site every day," it explained, in an emailed statement. "Subreddits are quarantined only when the content is clearly offensive to the broader Reddit community."

Quarantining aims to prevent the content from being accidentally viewed by those who do not wish to do so.

"A subreddit is quarantined when there are concerns that its content is extreme and could be offensive to people outside of that community," explained Reddit. "The quarantine process doesn’t end the conversation; it adds an opt-in measure so that people have the choice to join the conversation," it added.

Restrictions on a quarantined subreddit include requiring an explicit opt-in, requiring an account with a verified email address, no use of custom images and the removal of revenue generation.

Related: Reddit updates content policy, bans a 'handful' of groups that exist 'solely to annoy' others

The ‘european’ quarantining prompted a mixed reaction elsewhere on Reddit. Some users say that racist views were expressed on the subreddit, while others say that it hosted a range of opinions and cite the importance of open dialogue.

Reddit, which had over 277 million unique visitors last month, uses teams of volunteers to moderate subreddits.

The forum updated its content policy last year, consolidating multiple rules and policies into a single set of guidelines.

A blogger with an interest in numbers, who uses the name Curious Gnu, recently crunched a Reddit dataset of 4.6 million comments and noted that 78 percent of Reddit threads with over 1,000 comments mention Nazis or Hitler. The blogger found that around 2.6 percent of comments in the ‘european’ subreddit mentioned Nazis or Hitler. A slightly higher percentage of comments on the ‘AskHistorians’ subreddit mentioned Nazis or Hitler, with around 2.75 percent of comments on the ‘history’ subreddit referencing the topics.

Related: No censorship in Chinese Internet, says China's top censor

Reddit prohibits illegal content, spam, publication of someone’s private and confidential information, sexually suggestive content featuring minors and anything that incites harm or violence against an individual or group of people. Content that harasses, bullies, or abuses individuals or groups is also banned.

The Associated Press contributed to this report.