Facebook has removed campaign ads funded by the Trump campaign due to the use of a symbol previously used by Nazis to identify political prisoners in concentration camps.
The symbol, an inverted red triangle, was used in a Trump campaign ad to denounce Antifa, a large anti-fascist movement that Trump claims is responsible for violent protests in the United States.
Facebook said in a statement that the ad "violated their policy against organised hate."
"We don’t allow symbols that represent hateful organisations or hateful ideologies. You obviously want to be careful to allow someone to put up a symbol to condemn it or to discuss it," said Nathaniel Gleicher the head of security policy at Facebook at a US congressional hearing.
"But in a situation where we don’t see either of those we don’t allow it on the platform and we remove it. That’s what we saw in this case with this ad."
A Trump campaign associated Twitter account responded that the symbol was an emoji and "widely used by Antifa" something that experts have disputed.
The campaign also said the symbol was not in the Anti-Defamation League (ADL)'s database of symbols of hate.
The ADL said the triangle was not in its database because it is a historical symbol and the database contains symbols currently used by modern-day extremists and white supremacists.
"The Nazis used red triangles to identify their political victims in concentration camps. Using it to attack political opponents is highly offensive," said Anti-Defamation League president Jonathan Greenblatt in a tweet.
"[President Trump's] campaign needs to learn its history, as ignorance is no excuse for using Nazi-related symbols."
Facebook has faced criticism for not removing posts viewed as hate speech and for not labelling posts by Trump that spread misinformation.
Also on Thursday, Twitter labelled a video posted by the US President as "manipulated media" because it had doctored a video of two toddlers as a fake CNN report.
Twitter began flagging Trump tweets with fact checks last month.