French and Italian archaeologists have found the remains of a grain port that played a critical role in the rise of ancient Rome, France's National Centre for Scientific Research (CNRS) said on Thursday.

Cores drilled at a location at the mouth of the River Tiber have revealed the site of a port whose existence has been sought for centuries, it said in a press release.

The port lies northwest of Ostia, which was established by Rome as a fortress gateway to enable trade to pass upriver towards the city and prevent pirates and marauders.

The evidence points to a port established between the fourth and second century B.C. with a depth of 6 meters (20 feet), making it accessible to sea-going vessels, the CNRS said.