The controversy began shortly after the Italian team won the women's 4x400m relay at the Mediterranean Games in Tarragona, Spain, on Saturday night.
Italy's Maria Benedicta Chigbolu, Ayomide Folorunso, Raphaela Lukudo and Libania Grenot completed the race in 3 minutes and 28.08 seconds, more than a second ahead of France in second place and Spain in third.
The four athletes were photographed celebrating with an Italian flag, in a shot that quickly attracted attention.
Per una settimana non ho aperto né social né quotidiani. Vi racconto perché oggi nella #ENews. La notizia più bella di ieri, intanto, arriva dai Giochi del Mediterraneo, non da Pontida. Vince l’Italia che non ha paura: #PrimeLeItaliane— Matteo Renzi (@matteorenzi) July 2, 2018
Buon Luglio, amici pic.twitter.com/bSxfSDp2Tm
Matteo Renzi, former prime minister and ex-leader of the centre-left Democratic Party, shared it with the hashtag "Italian women first", a take-off of the "Italians first" slogan adopted by the anti-immigration League party that is the junior partner in Italy's coalition government.
"The best news yesterday came from the Mediterranean Games, not Pontida," Renzi wrote, referring to the northern Italian town where the League was holding a triumphant party rally, at which its leader Matteo Salvini called for a Europe-wide alliance against mass immigration.
Two of the winning athletes were born outside Italy and three are naturalized Italians. Only one, Chigbolu, has citizenship via a parent, the others having obtained it via marriage or ius soli, the "right of territory" that entitles those born or raised in Italy by foreign parents to eventually become Italian.
"Victory for the Italy that's not afraid," Renzi tweeted, in comments echoed by several other politicians on the left.
Ai #GiochidelMediterraneo oro italiano nella 4×400 grazie a Libania Grenot, Maria Benedicta Chigbolu, Ayomide Folorunso, Raphaela Lukudo. I loro sorrisi sono la risposta all’Italia razzista di Pontida. L’Italia multiculturale nata dal sogno repubblicano non verrà fermata. pic.twitter.com/oNaNq8LKJN— Roberto Saviano (@robertosaviano) July 1, 2018
Roberto Saviano, the author of mafia exposé Gomorrah and a prominent critic of Italy's new government, joined the congratulations, tweeting: "Their smiles are the riposte to the racist Italy of Pontida. The multicultural Italy born from a republican dream will not be stopped."
The celebrations didn't sit well with some of the League's supporters. "The real racists are the people forgetting all the other athletes winning medals at the Mediterranean Games," said Agricultural Minister Gian Marco Centinaio, a party member and close ally of Salvini.
"Well done to ALL Italian athletes."
https://t.co/DkGPo7tysL i veri razzisti sono quelli che si dimenticano di tutti gli altri atleti che hanno vinto delle medaglie ai giochi del mediterraneo. bravi a TUTTI gli atleti italiani #savianovaialavorare— gian marco centinaio (@giamma71) July 2, 2018
Salvini, however, congratulated the relay team and said he'd like to meet them in person "and give them a hug".
The interior minister, who led the charge to stop reforms that would have simplified the lengthy process of applying for Italian citizenship via ius soli, said that his problem wasn't with "young men and women, whatever their skin colour, who are helping our country to grow" but with "hundreds of thousands of clandestine immigrants".
Three members of the relay team, Chigbolu, Grenot and Folorunso, represented Italy in the same event at the 2016 Rio Olympics, where they placed sixth – albeit with a better time than last weekend's. Cuban-born Grenot is currently the European champion in the solo 400m and the first Italian woman to win an international track title in over 70 years.
They are among more than 100 Italian athletes to win 156 medals at the Mediterranean Games so far, where Italy is currently top of the medal table.
Part of the reason their victory has attracted so much attention is the relative dearth of prominent Italians of colour. With historically less immigration from Africa than other European countries such as France or the UK, people of African heritage still make up a small, though growing, fraction of the Italian population.
Footballer Mario Balotelli, one of the country's best known black athletes, recently called on Italy to "wake up" to racism after being subjected to abuse from his own team's fans.
Meanwhile Italy has only ever had one non-white member of cabinet, Cécile Kyenge, who weathered a torrent of racist abuse from members of the public and fellow politicians during her time as minister of integration.
And only in the last election did Italy elect its first black senator, Nigerian-born Toni Iwobi, who ran for the League on an anti-ius soli ticket.