Manchester United have condemned the "mindless idiots" who racially abused Axel Tuanzebe and Anthony Martial on social media and have called for stronger measures "to prevent this kind of behaviour".
Ole Gunnar Solskjaer's men fell to a shock 2-1 loss to the Premier League's bottom side Sheffield United at Old Trafford on Wednesday.
That defeat sparked a torrent of online abuse aimed at United's players, including racist abuse aimed at defender Tuanzebe, who inadvertently turned home Oliver Burke's winner, and forward Martial.
Racist terms and monkey emojis were put on Instagram comments of the pair's most recent posts.
United said in a club statement: "Everyone at Manchester United is disgusted by the racial abuse received by players via social media after last night's game.
"We utterly condemn it and it is encouraging to see other fans condemn this on social media also.
"Manchester United has zero tolerance of any form of racism or discrimination and a long-standing commitment to campaigning against it through our All Red All Equal initiative.
"Identifying these anonymous mindless idiots remains problematic. We urge social media platforms and regulatory authorities to strengthen measures to prevent this kind of behaviour."
Harry Maguire, Scott McTominay and Brandon Williams were among those to post on social media in support of their team-mates, while Kick It Out have labelled racist abuse "completely unacceptable".
Kick It Out chair Sanjay Bhandari said: "We are disappointed that players are continuing to be subject to racist abuse on their social platforms, it is completely unacceptable.
"We will continue to work with the football authorities, law enforcement and social media companies to try and rid football of hateful and discriminatory behaviour.
"As we have said before, online hate must have real-life consequences, so people don't continue to spread hate as freely as they wish. The individuals responsible for this abuse will hopefully be identified by the social media platforms and swiftly removed.
"We know that discriminatory abuse can have significant real world impact on the welfare of the victims. We encourage the players to get such support from their club in the first instance, and support is also available from the PFA and Kick It Out."
Following the online abuse, United midfielder McTominay posted a photo of Tuanzebe with a crown on his head alongside a heart emoji as well as black and white fists.
"My brother," he said on an Instagram Story post. "Disgusted with what I have read this morning"
United captain Maguire wrote on Twitter alongside a picture of the players taking a knee: "UNITED against racism. We will not tolerate it."