Twitter Chief Executive Jack Dorsey apologized Thursday after the microblogging service let through an ad promoting a white supremacist group.
“We made a mistake here and we apologize. Our automated system allowed an ad promoting hate. Against our policy. We did a retro and fixed," Dorsey tweeted.
The ad promoted an article titled "The United States Was Founded as a White People's Republic." It showed eight white children in a field.
It was tweeted from an account with the handle "@NEW_ORDER_1488."
Twitter has suspended several accounts linked to the alt-right movement, USA Today reported Wednesday.
The company, which has also been under criticism for not doing enough to thwart cyberbullying, said Tuesday that it would upgrade some features to curb abusive behavior.
Twitter's advertising policy prevents advertisers from promoting certain sensitive topics, including hate speech or discrimination against race, ethnicity, color, religion or sexual orientation.