Lukaku's second-half penalty secured Inter's victory, however the match was marred by monkey chants coming from fans behind the goal as the striker prepared to take his kick. 

He glared back at the supporters in question instead of celebrating after converting and it was the latest in a string of such incidents involving Cagliari and the fourth high-profile occasion in just over two years.

In May 2017, Pescara's Sulley Muntari was booked for complaining to the referee about racist abuse from Cagliari fans, later being given a one-match ban for walking off the pitch in protest. The club avoided punishment because "approximately 10" people were involved.

Juventus midfielder Blaise Matuidi claimed in January 2018 he was abused away to Cagliari and last season his then team-mate Moise Kean was targeted, the Sardinia club escaping punishment because Serie A felt the chants "had an objectively limited relevance to race".

Despite the regularity of such incidents, Cagliari denounced "silly" stereotypes of its fans.

"Cagliari Calcio firmly rejects what happened Sunday night at the Sardegna Arena during the game vs. Inter," the statement began.

"The club underlines - once again - its intention to identify, isolate and ban those ignorant individuals whose shameful actions and behaviours are completely against the values that Cagliari strongly promotes in all their initiatives. Every single day.

"Cagliari does not want to underplay what occurred, endorses the respectable moral values of its people from all the stadium sections, but firmly rejects the outrageous charge and silly stereotypes addressed to Cagliari supporters and the Sardinian people, which are absolutely unacceptable."

Lukaku released a statement calling for greater action from social media and federation stakeholders, which Cagliari echoed.

"Full solidarity to Romelu Lukaku and even stronger commitment towards annihilating one of the worst plagues that affects football and our world in general," the statement continued.

"However, as we are aware that technology is not enough, we believe our commitment needs a real support by the rest of the football stakeholders; starting from all the true supporters, to all the stewards in the stands; from police and security agents, passing to media and as well through Lega Serie A and FIGC [Italian Football Federation].

"Cagliari is asking you all [for] solid help to win a battle that involves everyone. No one excluded."