Greece has condemned an airstrike on a Greek-operated oil tanker moored off the Libyan coast that killed two of its crew members.

Araevo, which is Liberian-flagged and operated by Athens-based Aegean Shipping Management, was bombed at 1.30pm local time (7.30am EST) on Sunday while it lay at anchor two miles from the Islamist-controlled port of Derna in eastern Libya. A 29-year old Greek citizen and a Romanian died in the attack.

Two other members of the ship's crew of 26 — three Greeks, 21 Philipinos and two Romanians — were wounded, the Hellenic Coast Guard said in a statement after a briefing from the ship's management. Aegean Safety manager Elias Syrros told VICE News that Araevo was carrying 12,600 tons of crude oil, but that none of the cargo had leaked.

The Greek foreign ministry described the attack as "unprovoked and cowardly" on Monday, and said it was attempting to clarify the conditions under which it took place in order to identify and punish the perpetrators then seek compensation for the victims' families.

The Greek coastguard described the attacking aircraft as unidentified, while the foreign ministry avoided apportioning blame. However, a spokesperson for Libya's internationally recognized government said that Araevo had been bombed by its forces because it had refused to stop for cargo checks. The vessel's crew dimmed its lights before entering port "and because of this, it and its cargo were considered suspicious," said armed forces spokesman Colonel Ahmed Mesmari, according to Agence France-Presse.

However Syrros said that the vessel had in fact been stationary since January 2 and described the attack as "unprovoked and without any previous sign."

The Greek foreign ministry added that Araevo was leased to Libya's National Oil Corporation (NOC) and was following the same route between Libyan ports of Marsa al-Brega and Derna as it had done for years.

Libya is currently split between rival governments. One, the Tobruk-based Council of Deputies, is recognized by the international community and was set up after June elections as a replacement for the interim General National Congress (GNC) that governed after the ouster of longtime autocrat Muammar Qaddafi. However, the Islamist factions that had dominated the GNC, but fared badly in the voting, refused to accept the Council of Deputies' authority and set up a rival government in the capital Tripoli.

Islamist and nationalist militias have since clashed for control of the country in an ongoing crisis that has killed hundreds, displaced tens of thousands, and left the country in turmoil. Oil ports and infrastructure have become a major part of the battle between the two sides, which also have rival energy ministries. Nationalist forces have carried out a number of airstrikes on positions of the Libya Dawn Islamist alliance and other Islamist targets.