Facebook removed campaign ads for Donald Trump for using a Nazi symbol, the company said on Thursday.

The ads featured an upside-down red triangle, the same symbol that was once used by the Nazis to identify political prisoners, communists and other political prisoners in concentration camps.

Facebook's head of security policy, Nathaniel Gleicher, told a House Intelligence Committee that the ads were removed because Facebook does not permit symbols of hateful ideology "unless they're put up with context or condemnation."

"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, and anywhere that that symbol is used, we would take the same action," Gleicher said.

Read more: How does Twitter's tweet labeling work?

Antifa

Trump's communications director, Tim Murtaugh, said that the ads, which started on Wednesday, used the inverted red triangle because it was a symbol used by Antifa.

He said the symbol is not included in the Anti-Defamation League's database of symbols of hate.

"But it is ironic that it took a Trump ad to force the media to implicitly concede that Antifa is a hate group," he added.

Trump has targeted Antifa, meaning antifacist, alleging without evidence that it is a hate group that has incited violence, particularly during recent Black Lives Matter protests.

''Highly offensive'

Jonathan Greenblatt, chief executive of the Anti-Defamation League said on Twitter: "The Nazis used red triangles to identify their political victims in concentration camps."

"Using it to attack political opponents is highly offensive. POTUS' campaign needs to learn its history, as ignorance is no excuse for using Nazi-related symbols."

A spokesman for the ADL said its database was not meant to cover historical Nazi symbols, but those "commonly used by modern extremists and white supremacists in the United States."

He said that there had been isolated incidents of Antifa using the symbol, but that it was not a particularly common symbol used by the group.

Watchdog group Media Matters said in a response to a tweet from a "Trump War Room," that the symbol was certainly not widely used by Antifa.

The Facebook ads ran on pages belonging to Trump and Vice President Mike Pence. They also appeared in ads and posts on the "Team Trump" page.

The hearing focused on efforts by big technology companies to stop the spread of misinformation. Facebook's Gleicher was joined by representatives of Twitter and Google.

Democrats asked Facebook and Twitter why they had not removed tweets by Trump referencing the shooting of looters and a doctored video showing House of Representatives Speaker Nancy Pelosi look intoxicated.

Facebook CEO Mark Zuckerberg has been the target of criticism for refusing to take action on inflammatory posts by Trump. 

Twitter recently posted a fact check beside a particularly egregious tweet by Trump, deeply angering him.

aw/sri (AP, AFP, Reuters, dpa)