Facebook Inc's independent Oversight Board announced on Tuesday the first six cases where it could overrule the social media company's decisions to remove certain pieces of content from its platforms.

The board, which Facebook created in response to criticism of its handling of problematic content, said it had received 20,000 cases since it opened its doors in October.

Three of the six cases involved content that Facebook removed for breaking hate speech rules.

An Oversight Board spokesman said hate speech cases had been "the most significant proportion" of appeals received.

"Hate speech is an especially difficult area," Jamal Greene, one of the board's co-chairs and a professor at Columbia Law School, told Reuters in an interview. "It's not that easy ... for an algorithm to get the context of" such speech.

In November, Facebook for the first time disclosed numbers on the prevalence of hate speech on the platform, saying that out of every 10,000 content views in the third quarter, 10 to 11 included hate speech. 

The global board's other chosen cases involved content removed from Facebook or Instagram for violating rules on adult nudity, dangerous individuals and organizations, and violence and incitement. Greene said they raised "important line-drawing questions." 

One case was submitted by Facebook itself. The company said this case highlighted the challenge it faced when dealing with the risks of offline harm caused by misinformation about the COVID-19 pandemic.

Facebook can also ask the board for non-binding policy recommendations, but Greene said it had not yet done so.

The board has opened a week-long public comment period on the first cases, which will be reviewed by five-member panels. There is a 90-day deadline for decisions on the cases to be reached and for Facebook to act on them. 

The board, which has been criticized for its limited remit, aims to start hearing cases from users in early 2021 about content that has been left on the site as well as taken down.

This week, a group of Facebook critics dubbed "The Real Facebook Oversight Board" said it would hear three cases not yet eligible for users to take to the official oversight board, including a dispute about the Facebook account of Steve Bannon, President Donald Trump's former adviser. 

Asked about this group, a spokeswoman for Facebook's Oversight Board said: "Lots of people have opinions about Facebook. The Oversight Board is focused on making binding decisions and issuing policy recommendations that will hold Facebook to account."

(Reporting by Elizabeth Culliford; Editing by Edmund Blair) ((elizabeth.culliford@thomsonreuters.com; 2127679959;))