Striker Romelu Lukaku says "we are going backwards" on racism after he was racially abused by Cagliari fans while playing for Inter Milan on Sunday.

It follows incidents where Manchester United's Paul Pogba and Marcus Rashford, and Chelsea striker Tammy Abraham were abused on social media.

"As players we need to unify and make a statement on this matter," Lukaku said.

Cagliari said they were committed to "annihilating one of the worst plagues that affects football and our world".

In a statement the club, whose fans have been involved in a number of racist incidents, said they were in "full solidarity" with Lukaku and pledged to "identify, isolate and ban" the "ignorant individuals whose shameful actions and behaviours are completely against" the club's values.

Serie A - which expressed "firm condemnation" of the incident - is investigating the racist abuse, which came when Lukaku scored the winning goal in a 2-1 away victory.

After scoring a 72nd-minute penalty the former Manchester United striker stood and stared at fans behind the goal - where monkey chants had come from.

"Many players in the last month have suffered from racial abuse… I did yesterday too," Lukaku in his statement.

"Football is a game to be enjoyed and we shouldn't accept any form of discrimination that will put our game in shame.

"Ladies and gentlemen it's 2019 - instead of going forwards we're going backwards.

"I hope the football federations all over the world react strongly on all cases of discrimination.

"Social media platforms (Instagram, Twitter, Facebook) need to work better as well with football clubs because every day you see at least a racist comment under a post of a person of colour. We've been saying it for years and still no action."

Lukaku's former United team-mates Pogba and Rashford were both targeted on social media after penalty misses this season.

Chelsea defender Kurt Zouma was racially abused on Saturday after an own goal against Sheffield United, while team-mate Abraham and Reading's Yakou Meite both received racist messages online after missing penalties last month.

England women's manager Phil Neville said footballers should "boycott" social media and Chelsea boss Frank Lampard said social media companies needed to do more.

Last month, Twitter said it would meet clubs and campaigning organisations to show the "proactive work" being done to tackle abuse.