Two crew members were killed when unidentified military aircraft bombed a Greek-operated oil tanker anchored at the Libyan port of Derna, the Greek coastguard said.

The Liberian-flagged ARAEVO was carrying 12,600 tons of crude oil and had 26 crew members on board. Two other crew members were wounded, the coastguard said.

Athens-based Aegean Shipping Enterprises Co, which operates the vessel, said no oil had spilled as a result of the attack. The vessel, chartered by Libya's national oil company NOC, had been loaded at Brega port for transport to Derna.

"Yesterday at 13:30 local time, a war plane bombed the front part of the ship, causing damage and injuring four crew members, of whom two died," said Elias Syrros, the company's safety manager. "There is no oil leakage, the ship's integrity was not compromised. Damages are being assessed."

An industry source said the vessel was delivering gasoil to power generators that supply the cities of Derna, Khoms, Benghazi and Misrata.

Forces loyal to Libya's internationally recognized government have been carrying out air strikes on targets controlled by a rival government set up by Libya Dawn forces that have taken over the capital Tripoli.

Oil ports have become part of the battle between the rival factions for control of Libya.

A spokesman for chief of staff for the internationally recognized government said the tanker had been bringing Islamist militant fighters into Derna

"We had warned any ship not to dock at the port without prior permission," Ahmed Mesmari said.

The self-declared government in Tripoli and the internationally recognized government have appointed rival officials in the oil ministry and NOC, leading to competing claims over control of the OPEC nation's petroleum assets.