The attack is reported to have happened at a house party in Marconia di Pisticci in the Basilicata region and involved eight young men. A local judge has said the attack involved “serious and brutal violence”. The four men, aged between 19 and 23, are accused of rape and grievous bodily harm.
They are all from the Pisticci area.
Three other suspects are under investigation, while an eighth is yet to be identified.
The girls, whose ages are not known, are said to have been attacked at a villa in the town on Monday night, where they had been invited to a birthday bash.
Local media reports said the girls, who do not speak Italian, befriended one of the attackers who later took advantage of them after they had consumed alcohol.
Angelo Onorati, a prosecutor in the Matera region, ordered the arrests owing to the “brutality, severity and savagery of the violence committed, in devious ways, that could be repeated against other women”.
Reports in the local press said the victims had been slapped and punched before being raped by more than one man.
The attack is said to have happened in the garden of the villa.
Officers have released CCTV footage showing one of the girls being pushed by a group of males towards a dark corner behind the villa.
READ MORE: Horror as British tourist ‘raped and robbed by gang of men in Milan’
They were admitted to the Madonna della Grazie hospital in Matera.
Doctors discovered marks on their bodies showing signs of violence, reports suggest.
The news agency Adnkronos reported that the victims had since been discharged from hospital.
On Thursday police in Matera said: “On the night between 7-8 September, in Marconia di Pisticci, sexual violence was committed against two foreign minors who were at a party in a villa.
“The investigative unit of Matera police headquarters has begun investigations in coordination with the public prosecutor’s office.”
A lawyer representing the girls said the attack was “unprecedented” in the area.
Giuseppe Rago told Adnkronos: “They are girls with a strong character, they have been heartened by their families and are confident in the work of justice.
“They hope to soon recover and forget what happened.
“We would never have thought that such wickedness could happen here.”