Bananas were thrown at Italy's first black minister, Cecile Kyenge, at a political rally, in the latest of a series of racial slurs and threats the politician has been subjected to since taking office.

The integration minister was addressing a political rally in Cervia, when a man in the crowd threw two bananas, narrowly missing the stage, Kyenge's spokesman Cosimo Torlo said.

"I was able to verify which levels can be reached by human stupidity," wrote Giancarlo Mazzuca, editor of Il Giorno, who was sitting two seats from Kyenge at the time.

Kyenge responded to the insult on Twitter, calling it "sad" and a waste of food when so many are dying of hunger.

"The courage and optimism to change things has to come above all from the bottom up to reach the institutions," she said.

Police said they are looking for the culprit and that Kyenge will be given increased security.

Recently, anti-immigration Northern League senator Roberto Calderoli only apologised after a storm of criticism when he said that Kyenge looked like an Orangutan.

In June, a Northern League local councillor called for Kyenge to be raped so she could understand how the victims of sex crimes committed by immigrants feel.

Just before the incident on Friday, mannequins soaked in fake blood were left nearby, clutching leaflets saying "immigration kills," a slogan used by the far-right Forza Nuova group, which claims that immigrants are responsible for crime. The group has since admitted putting them there.

Politicians rallied to defend Kyenge.

Education Minister Maria Chiara Carrozza praised Kyenge for her courage and determination in such a hostile climate.

Environment minister Andrea Orlando said on Twitter he felt "utmost indignation for this lowly act".

Veneto governor Luca Zaia, of the Northern League, also condemned the gesture.

"Throwing bananas, personal insults ... acts like these play no part in the civilised and democratic discussion needed between the minister and those who don't share her opinion," the ANSA news agency quoted him as saying.

With unemployment in Italy at its highest level for 20 years, some commentators think that Italians are increasingly focusing their anger on immigrants.

"The economic crisis is worsening the situation," he said. "Jobs that until a few years ago wouldn't have even been considered by Italians are now becoming precious," Mazzuca told CNN.

Italy is currently facing a crisis of race relations. Recently, AC Milan player Kevin Constant walked off the pitch when he was subjected to racial abuse from fans in a game against Sassuolo. His team-mate Kevin Prince Boateng also walked off during a game with Pro Patria after being racially abused.