A tanker with oil from eastern Libya returned with its cargo to the North African country after the United Nations blacklisted the shipment, amid an escalating struggle between the nation’s rival governments for control of its crude wealth, Bloomberg reported.

The UN Security Council added the vessel to its sanctions list after the Mediterranean island of Malta refused to let the tanker Distya Ameya dock there. The NOC in Tripoli called the shipment illegal and informed Libya’s newly formed UN-backed unity government about the eastern government’s attempt to export oil independently.

Two competing governments, one in Tripoli and one in the east, backed by armed factions have struggled for control of the North African OPEC state since 2014, as Reuters wrote. The eastern administration has set up its own National Oil Corporation in parallel to the Tripoli-based NOC.

In fact, western powers fear any attempt by the eastern NOC to export crude independently would undermine the Tripoli government and further fracture the country along regional lines. “This episode is a clear warning to all ship owners and trading companies that oil exports from Libya by any other entity than the National Oil Corporation of Libya are illegal and will be stopped,” the NOC Chairman Mustafa Sanalla said in a statement.