Five police officers in northern Italy have been placed under house arrest pending an inquiry into allegations that they beat and tortured detainees, most of them migrants, according to local media.

An inspector and four officers in Verona, northeast Italy, are accused of beating and insulting people held in custody, La Stampa daily reported on Wednesday.

A dozen of their colleagues are also under investigation for having allegedly done nothing to stop the abuse, the report added.

La Stampa cited a former prisoner, a Romanian, who said officers had forced him to urinate in a corner of his cell at a police station in Verona, having refused to let him use the toilet.

Afterwards, they beat him up and dragged him over the floor where he had had to urinate, to punish him.

"If these facts are confirmed, it would be enormously serious," Interior Minister Matteo Piantedosi said on Wednesday.

Such conduct damaged "not just the dignity of the victims but also the honour and the reputation" of thousands of honest police officers, he added.

Late last month, a Brazilian national sued police officers in Milan for alleged brutality, after they beat her in an incident recorded in a video that went viral online.

It showed three officers using their batons to strike the 41-year-old on the head and in the ribs while spraying her with tear gas as she sat in the street, her hands raised.

Prosecutors have opened an investigation into the incident.