The master of a Cotunav ro-pax that slammed into a boxship last year was talking on the phone away from radar screens at the time, a joint probe has claimed.

The 17,900-gt Tunisian-owned Ulysse (built 1997) hit Cyprus Sea Lines' (CSL) anchored 5,018-teu CSL Virginia (built 2005) off Corsica in October.

An investigation by Tunisia, Cyprus and France found the accident was caused by human error, with faults on both sides, AFP said.

Youssef Ben Romdhane, Tunisia’s director general of shipping and ports, told AFP: “The captain of the Tunisian boat was busy, making private telephone calls. He was far from the radar screen that warns of danger. He was alone,” he said.

The Realites website cited Ben Romdhane as saying: "The investigation proved that the ship's captain did not pay attention and was not vigilant enough.

"He was busy with phone calls and a personal SMS exchange. His mind was elsewhere. He saw the CLS Virginia at a distance of 20 miles. Yet he kept the same speed of navigation and he did not change direction."

He also said it was unusual for the boxship to be anchored in a shipping lane.

Cotunav and CSL have been contacted for comment.

A separate French investigation is still ongoing.

About 200 cbm of fuel was spilled in the incident.

The ferry was en route from Genoa to Rades in Tunisia. CSL Virginia was not carrying any cargo.

A simulation using AIS data by MarineTraffic showed the ferry maintaining a straight course and ploughing into the boxship at 19 knots.

The boxship has since been renamed Virgin Star under the ownership of Virgin Maritime.