There was no eyewitness report or independent confirmation for the strike near the town of Mareesa that was also reported by the Dubai-based Al-Arabiya television network.
“The vessel was sunk because it had loaded fighters, weapons and ammunition to support terrorism in the eastern region,” air force spokesman Nasser al-Hassi said early on Monday.
Mohamed El Hejazi, a spokesman for Khalifa Haftar, top army commander of the official government based in eastern Libya, said the strike had also targeted a second vessel which had been carrying weapons in the same area.
A Reuters reporter had on Sunday heard war planes circling above Benghazi, which is about 20 km (12 miles) from Mareesa.
Tripoli-based state oil firm NOC has accused the eastern government of having three times bombed oil tankers that the eastern forces had said carried weapons and ammunition.
Libya is in chaos, with two governments and parliaments with their own armed forces fighting for control four years after the ouster of Muammar Gaddafi.
The official government is based in the east since losing the capital a year ago to a rival group, which set up its own administration. Both have attacked each other with aircraft.
In May, planes from Libya’s recognized government attacked an oil tanker docked outside the central city of Sirte, wounding three people and setting the ship on fire.
In January, Greece complained about the bombing of a Greek-operated tanker anchored off the Libyan coast that killed two crewman. Greece said it said was carrying heavy fuel, while Libya’s official government said it was carrying weapons.
Both governments control limited territory in the oil producer. Islamic State militants have exploited a security vacuum to expand in Libya, beheading and kidnapping foreigners while also attacking foreign missions in Tripoli and fighting with forces of both governments.
France 24/ REUTERS