AC Milan striker Kevin-Prince Boateng stormed off the pitch after racist chants from a group of fans on Thursday, forcing a friendly away game against fourth-tier club Pro Patria to be suspended.

"Shame that these things still happen," the 25-year-old German-born Ghanaian player said on his Twitter account after the match was stopped in the 26th minute when he led his team off the pitch.

Sports daily Gazzetta dello Sport said it was the first time in Italy that a football game had been suspended because of racist chants.

Boateng picked up the ball, kicked it towards the stands and walked off the pitch in Pro Patria's home town of Busto Arsizio near Milan.

His teammates walked off after him despite Pro Patria players begging them to stay and whistles from most of the home fans against the racists.

The referee had already suspended the game twice before Boateng's outburst for repeated insults against the striker and fellow black teammates Sulley Muntari, M'Baye Niang and Urby Emanuelson.

"Pulling out was the right choice with something like this," said Milan coach Massimiliano Allegri.

"We have to stop it with these uncouth acts. Italy as a country has to improve and become more civilized and intelligent," he told reporters.

Captain Massimo Ambrosini added: "That was intolerable, it was only a friendly. We couldn't have gone on like that, we had to give a signal."

There were many expressions of support for Boateng's unprecedented move from football fans on social media networks, as well as from Italy's football federation president Giancarlo Abete who spoke of a "resurgence of racial discrimination."

"This was an unspeakable and intolerable incident," said Abete, calling on federation prosecutors to work together with police and identify the racists.

"The racist behaviour of these so-called fans ruined a friendly game that was meant to be a feast of football in Busto Arsizio," he said.

But town mayor Gigi Farioli said Boateng's reaction had been "inappropriate" and he should have been sent off for "kicking a ball at 200 kilometres an hour towards a fan".

Farioli, a member of Silvio Berlusconi's People of Freedom party, said he had been at the game and "heard nothing" from the stands.

"I was told there were three or four idiots who maybe were not even from Busto who shouted a few boos at the players," he said.

Boateng, who played for Ghana at the 2010 World Cup, was previously at Tottenham, Borussia Dortmund and Portsmouth.

Berlusconi's daughter Barbara, an AC Milan board member and the girlfriend of the club's Brazilian forward Alexandre Pato, voiced support for Boateng.

"There should be zero tolerance for incidents like this. The games should be suspended immediately, also in the championship," she said.

"We can't always pretend not to see and not to hear."

Racism has been a constant problem in Italy's stadiums and football chiefs have been accused of not doing enough to tackle the problem.

In November last year Italian football bosses offered an apology for an apparent anti-Semitic attack against Tottenham fans in Rome that left several supporters in hospital.

England's Football Association also said it would urge UEFA to investigate allegations of anti-Semitic chanting during Tottenham's Europa League game at Italian club Lazio.