IBM has suspended advertising on X, formerly known as Twitter, after a report said its ads were placed next to posts praising Adolf Hitler and Nazism.
The company said it was “completely unacceptable” that its content appeared in such threads on the platform.
X said it does not intentionally place brands “next to this kind of content”.
It comes as X owner Elon Musk was criticised after calling an antisemitic conspiracy theory “actual truth” when replying to a post on the platform.
The left-leaning watchdog Media Matters for America said it found ads bought by IBM and other companies next to posts including Hitler quotes, praise of Nazis and Holocaust denial.
X said in a statement to the BBC that one pro-Nazi post that was shown next to an IBM ad was seen about 8-thousand times.
The other firms listed include Apple, Oracle, television network Bravo and telecoms company Xfinity.
The BBC has approached the companies for comment.