Donald Trump has criticised social media companies after Facebook banned a number of extremist figures, declaring that he was “monitoring and watching, closely!!”

The US president, who tweeted and retweeted complaints on Friday and Saturday, said he would “monitor the censorship of AMERICAN CITIZENS on social media platforms”.

He has previously claimed social media companies are biased against conservatives, something the companies have rejected as untrue.

His comments came after Facebook this week banned Louis Farrakhan, Alex Jones and other extremists, saying they violated its ban on “dangerous individuals”.

The company also removed right-wing personalities Paul Nehlen, Milo Yiannopoulos, Paul Joseph Watson and Laura Loomer, along with Mr Jones’s site, Infowars, which often posts conspiracy theories.

The latest bans apply to Facebook’s main service and to Instagram, and extend to fan pages and other related accounts.

Louis Farrakhan and Alex JonesLouis Farrakhan and Alex Jones (AP)

Facebook’s move signalled new effort by the social media giant to remove people and groups promoting objectionable material such as hate, racism and anti-Semitism.

The company said it has “always banned” people or groups that proclaim a violent or hateful mission or are engaged in acts of hate or violence, regardless of political ideology.

On Twitter, Mr Trump cited a number of individuals he said were being unfairly treated by social media companies, including Mr Watson and actor James Woods. He insisted it was “getting worse and worse for Conservatives on social media!”

Woods, one of Hollywood’s most outspoken conservatives, has had his Twitter account locked. Twitter spokeswoman Katie Rosborough said he will need to delete a tweet that violated Twitter rules before he can be reinstated.

“We enforce the Twitter rules impartially for all users, regardless of their background or political affiliation,” Ms Rosborough said.

The president, who uses Twitter extensively to push his message, recently met Twitter chief executive Jack Dorsey at the White House after attacking the company and complaining that it was not treating him well because he was a Republican. He later described it as a “great meeting”.