A Nigerian refugee thought to have fled the terrorist group Boko Haram with his wife has died after being attacked by an “ultra” football fan in a small Italian town.

Emmanuel Chidi Namdi, 36, died of injuries he sustained when a local man, who had reportedly been racially abusing Namdi’s wife, attacked him in the town of Fermo, in central Italy.

Amedeo Mancini, 39, allegedly referred to the 24-year-old woman as a “monkey”, and attacked Namdi when he attempted to defend her, according to Italian media reports. Namdi fell into a coma and was pronounced dead on Wednesday.

Some Italian news reports said friends of Mancini contended that he had to fight back because the Nigerian man tried to attack the Italian after his wife was insulted and dragged.

Other witnesses said the husband was struck, first with a street sign ripped out of the pavement, then kicked, when he sought to defend his wife, but didn’t strike first.

Police arrested Mancini, who has been described as an “ultra”, an extremist football fan. His lawyer, Francesco De Minicis, told the news agency Ansa that his client had not intended to kill the Nigerian.

“Amedeo Mancini is destroyed with pain. He did not want to kill, and he expresses his closeness to those who are crying for Emmanuel,” De Minicis said.

“My client did not expect that punching the migrant would have this effect, and he places the episode in a defensive context.”

The killing has shocked Italy and prompted senior government figures to speak out against hate crime. On Thursday the prime minister, Matteo Renzi, posted on Twitter: “Today the government is in Fermo with Father Vinicio and local institutions in memory of Emmanuel. Against hate, racism and violence.”

Il Governo oggi a Fermo con don Vinicio e le Istituzioni locali in memoria di #Emmanuel

Contro l'odio, il razzismo e la violenza. — Matteo Renzi (@matteorenzi) July 7, 2016

Namdi and his wife, identified by her first name, Chimiary, were being hosted by Fermo town’s parish while they sought asylum. They are believed to have fled from Boko Haram and travelled through Niger and Libya before boarding a boat to Italy.

Father Vinicio Albanesi, who was hosting the couple, said they had previously lost a two-year-old daughter, and that Namdi’s wife suffered a miscarriage during the journey to Italy.

At an evening vigil on Wednesday, Chimiary cried out to her late husband: “Why do you leave me in this wicked world?”

Refugees and migrants are hosted across Italy in centres run by the government or outsourced to private organisations and charities. Pope Francis has encouraged parishes to take in asylum seekers, and the Vatican has recently hosted a number of refugee families in Rome.

Nigerians make up 12% of the more than 70,000 people who have arrived in Italy by sea so far this year, the second-largest group by nationality after Eritreans.

The killing in Fermo prompted Italy’s interior minister, Angelino Alfano, to travel to the town to discuss public order and security.

Alfano insisted that Italy as a whole welcomed refugees and migrants. “Italy isn’t represented by Amedeo Mancini,” he said.

Laura Boldrini, the speaker in Italy’s lower house, said she felt dismay and indignation following the racist and xenophobic attack.

“The hate that poisons our society will be acknowledged and not underestimated … Those who have political and institutional responsibility must distance themselves from messages of hate and not stoke them,” tweeted Boldrini, who worked for the UN’s refugee agency, UNHCR, before entering politics.

L'odio che avvelena la nostra società va riconosciuto e non sottovalutato. Per questo ho costituito commissione parlamentare su #hatespeech — laura boldrini (@lauraboldrini) July 7, 2016

Her remarks point to Italy’s previous failures to stamp out racism in the highest realms of power. In September, lawmakers voted not to seek charges against a senator, Roberto Calderoli, who likened the country’s first black minister, Cécile Kyenge, to an orangutan.

Formerly the country’s integration minister, Kyenge was subjected to an aggressive campaign by the far right during her term, including nooses being hung up around a city she visited.

In 2014 the global football association Fifa handed down a six-month ban to the head of Italy’s FA, Carlo Tavecchio, for an alleged racist slur. Tavecchio was accused of describing a fictitious African player as “eating bananas”, an incident that caused international outrage, but did not prevent his subsequent election as president of the association.