The social media company X, formerly Twitter, sued media watchdog group Media Matters on Monday, alleging defamation after the group reported that the platform was placing ads for major brands next to pro-Hitler and white nationalist content.

The complaint alleges that Media Matters “knowingly and maliciously manufactured side-by-side images” that showed X ads next to racist content and presented them as if they were what “typical X users” see on the platform.

Filed in the Northern District of Texas federal court, the suit also names Media Matters senior investigative reporter Eric Hananoki as a defendant.

X Chief Executive Linda Yaccarino tweeted about the lawsuit Monday afternoon.

“Not a single authentic user on X saw IBM’s, Comcast’s, or Oracle’s ads next to the content in Media Matters’ article,” she wrote. “Stand with X.”

Media Matters first reported Thursday that ads placed by Apple, Bravo, IBM, Oracle and Xfinity had been served next to content supporting Hitler and the Nazi party. A follow-up report the next day found more ads from major brands next to white nationalist content. The organization has previously reported ad placements next to Holocaust denial and 9/11 conspiracy theory content.

Major advertisers such as Disney, IBM, Apple, Warner Bros. Discovery and Comcast paused advertising on X after the reports, which roughly coincided with X owner Elon Musk publicly endorsing a notorious antisemitic conspiracy theory blaming Jewish people for promoting immigration to disempower white Americans.

As the ad withdrawals mounted, Musk threatened to file a “thermonuclear lawsuit” against Media Matters late Friday, stating its reports were an “attempt to undermine freedom of speech and mislead advertisers.” The complaint called its reporting a “smear campaign.”

In a statement, Media Matters President Angelo Carusone responded, “This is a frivolous lawsuit meant to bully X’s critics into silence. Media Matters stands behind its reporting and looks forward to winning in court.”

Advertisers have been pulling back from the platform since Musk purchased Twitter in October 2022 and laid off hundreds of employees, decimating its teams overseeing content moderation and user safety.

In August, Yaccarino told CNBC that brands were “protected from the risk of being next to” toxic content and the company was working to reduce risk for advertisers.