Italy's defence minister has said there is "some basis" to allegations by two American students that they were raped in Florence by Carabinieri policemen.
The two women, aged 19 and 21, have said they were raped in the early hours of September 7 after they were given a lift home from a nightclub in the Italian city by a Carabinieri police patrol. The two policemen have denied the accusations.
Italian media say the police were called to the nightclub after a fight broke out on the premises. The students told investigators that two officers had offered to give them a ride back to their residence.
The students said they were raped inside the building before they could reach their rooms.
"Investigations are still ongoing, but there is some basis regarding the allegations," Defence Minister Roberta Pinotti told a conference on women's issues late on Friday.
"Rape is always a serious matter. But it's of unprecedented seriousness if it is committed by Carabinieri in uniform."
The Carabinieri is a paramilitary police force under the control of the Defence Ministry. It works alongside the national police, which is controlled by the Interior Ministry.
Italian media say the two women, who come from the states of Maine and New Jersey, told investigators they had drunk alcohol and smoked cannabis the night of the attack. They said they had been too frightened to scream or shout as the alleged assault took place.
Police are carrying out DNA tests to try to verify their accusations, with results expected in the coming days.
The case, which has received wide play in the Italian media, comes less than two weeks after a Polish tourist and Peruvian transsexual were brutally raped in the seaside resort of Rimini.
Two Moroccans, a Nigerian and a Congolese asylum seeker have been arrested over the attacks, which led to a sharp increase in anti-immigrant sentiment in Italy.
The allegations levelled against the Carabinieri have dismayed the Italian establishment.
"If this is true, and I hope that light is shed on the matter as soon as possible, then it would be an act of unheard of gravity," Tullio Del Sette, the head of the army, told the ANSA news agency.