The fans, reported by La Stampa to be part of the ‘Ultras’, an organized group responsible for much of the violence surrounding Italian football, said the person responsible for shooting Esposito, 30, would “pay, sooner or later”.

Emotions were running high during a game between Napoli and Cagliari at the San Paolo stadium in Naples on Wednesday night, where a minute of silence was held for Esposito, who underwent an operation to remove a bullet that was lodged dangerously close to his spine.

Although doctors said after the operation that he was “out of danger”, they operated again on Tuesday after Esposito suffered a cardiac arrest, Libero Quotidiano reported.

“He’s in a serious condition,” his mother, Antonella Leandri, was quoted as saying.

Daniele De Santis, also an ‘ultra’ and AS Roma fan, was charged on Sunday with attempted murder after allegedly shooting Esposito and two other Napoli fans ahead of the Italian Cup final between Napoli and Fiorentina.

Police sources told the Italian news agency Ansa on Tuesday that forensic tests on the 48-year-old found traces "compatible with gunshot material" , even though the results were partially negative.

The 48-year-old tested negative for gunshot residue, according to reports by the Italian news agency Ansa on Tuesday, but is still under investigation due to evidence from eye witnesses.

Although police said De Santis “acted alone”, those seeking revenge claim the attack was “premeditated” and involved “a group of 30”, La Stampa reported.

“Roman bastard” and “Rome is the enemy city” chants could be heard at the stadium last night, the newspaper said.

“They shot, they used guns because they were overwhelmed after their ambush failed,” the Ultras reportedly said.

De Santis, nicknamed Gastone, reportedly provoked the Napoli supporters using smoke bombs. When they reacted badly, he is said to have pulled out a gun and started shooting.

The violent attack was one of the worst seen in Italian football, but some say the authorities, despite pledges, have never really tackled the problem of hooligans.

“Soccer has long been a free zone, with no law, or rather without the state’s law — that of criminals and thugs has its full jurisdiction,” Maurizio Crosetti, a sports journalist, wrote on Sunday in La Repubblica.

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