England captain Owen Farrell says online abuse of team-mate Tom Curry for reporting an alleged on-pitch racial slur is "unacceptable".

World Rugby is reviewing the incident from the first half of the Rugby World Cup semi-final loss to the Springboks.

"What isn't understandable is the amount of abuse," said Farrell.

"The effect the abuse has - not just on him - is what I and we really don't understand.

"You are dealing with a human being, just because you are saying stuff on your phone or behind a screen doesn't make it acceptable.

"I hope he knows that everyone close to him supports him and backs him all the way. I am sure he does.

"The people close to him, I hope they know he is being supported really well."

England coach Steve Borthwick said that Curry has been preparing well for Friday's third-place play-off against Argentina despite the incident.

"Tom Curry has been the ultimate professional with his preparation this week, as he is every single day, every single week," Borthwick said.

"This is not a Tom Curry incident - someone has said something in the game that he has reported and he is getting on with preparing.

"This is a World Rugby and SA Rugby matter to deal with."

Sale offer support to Curry

Curry's club Sale Sharks say the 25-year-old has their full support.

"Sale Sharks' owners, players, coaches and staff are absolutely appalled by the nature and level of disgusting abuse directed at Tom Curry and his family in relation to an incident in the England v South Africa World Cup semi-final," said the Premiership club.

"Everyone at the club stands fully and proudly behind Tom and we look forward to welcoming him back to Carrington."

England flanker Curry was asked after the match whether something untoward had been said to him by Mbonambi.

"Yeah," he replied, before adding that "it does not need to be talked about".

The South African rugby union has also started its own investigation into Curry's claim.

"We are aware of the allegation, which we take very seriously, and are reviewing the available evidence," it said.

"We will engage with Bongi if anything is found to substantiate the claim."