The alleged attack took place on Monday night after a house party in the small seaside town of Marconia di Pisticci, local media reports.
The town is in the Basilicata province of Matera, one of southern Italy's biggest tourist destinations.
“The two victims were reportedly approached by two young men who seemed to have taken advantage of their physical state, possibly due to alcohol,” said
Pietro Argentino, public prosecutor in the nearby city of Matera.
“Two others arrived later and the rapes happened in a field next to the villa,” Argentino told the AGI news agency.
The girls, said to be teenagers, were hit before being raped by more than one person, according to local media reports.
Both aged around 15, they told their parents what happened when they later arrived home and were taken by ambulance to a hospital in Matera.
One of the girls is reported to have relatives living in the area who moved over from England several years ago.
Police arrested four men, all from Marconia di Pisticci and some of whom had criminal records. They are all between 19 and 23 years old.
Four other men are also being sought in the case.
“What happened is extremely serious, and we hope the judicial authority will do justice to the girls and their parents for what they had to endure,”
their lawyer Giuseppe Rago said.
“The girls are certainly not well,” he told the AGI news agency.