Haftar has been waging a deadly campaign since April 4 to seize Tripoli from troops aligned to Libya’s UN-recognized Government of National Accord (GNA).
The offensive has exacerbated chaos in Libya since the toppling of Muammar Gaddafi in 2011, threatening to plunge the country into a full-blown civil war, Presstv Reported.
Haftar's Libyan National Army (LNA) has almost two-thirds of the country and all oilfields under its control amid support from Saudi Arabia, the UAE and Egypt.
He also enjoys support of some Western countries, including France and Italy, because they believe he holds the future keys to Libya's oil spigots.
On Saturday, the LNA confirmed that it had sent a warship to the eastern Ras Lanuf oil port, after days of unconfirmed rumors of a foreign navy ship having been sighted.
LNA spokesman Ahmed Mismari told reporters that his forces had sent the Alkarama patrol vessel to Libya’s key Oil Crescent region as part of a “training mission” to visit the operations room and to secure oil facilities.
Haftar has repeatedly sought to take over oil exports from state oil firm NOC which is based in Tripoli and has sought to stay out of the conflict between the two parallel governments in Libya.
NOC gives export proceeds to the central bank which mainly works with the Tripoli government but also pays some public servants in LNA-controlled eastern Libya.
According to a UN report, the LNA last year had received the patrol vessel, which was previously owned by a firm with a postal address in the United Arab Emirates (UAE).
Supporters of the Tripoli government of Prime Minister Fayez al-Sarraj have also blamed UAE drones for airstrikes on the capital.
The UAE and Egypt have helped Haftar in the past with airstrikes and provided his forces with military equipment such as helicopters, even building an air base, UN reports have said.
Late on Saturday, airstrikes hit the capital where anti-aircraft fire was heard afterwards.
Haftar's offensive to seize Tripoli, however, has hit a brick wall and the Tripoli forces have pushed back the LNA on the ground in some southern suburbs in recent days.
Since Gaddafi's ouster in 2011, Libya has been divided mostly between two main rivaling powers, one linked with Haftar in the eastern city of Tobruk, and the other in Tripoli.
Gaddafi's ouster in the wake of a popular revolt and then NATO's military intervention has created a huge power vacuum, leading to chaos and the emergence of numerous militant outfits, including the Daesh terrorist group.