Gianni Gargano, mayor of Castelfranco Emilia, told the Polish news agency PAP that Italian agency Ansa had misquoted him, and that he had asked it to issue a correction.
Four of the eight victims were residents of his town, he said, among them a Polish woman who has lived in Italy for around 30 years, and three others with no Polish background.
Poland's foreign ministry spokesperson Maciej Wewiór said Italian authorities had identified two foreign nationals among the injured, including the Polish woman, with the remaining victims being Italian.
Poland's consul has been in contact with local services, police and the hospital where she is being treated.
Eight people were hurt in Saturday's attack, three of them seriously.
Italy's President Sergio Mattarella and Prime Minister Giorgia Meloni visited the injured in hospital.
The attacker, a 31-year-old man from a Moroccan immigrant family, was subdued by bystanders before being handed to police.
Reports say he had received psychiatric treatment.
He stabbed one of the men who restrained him.
His motive is not yet known.
(ał)
Source: PAP