TRIPOLI, June 22 (Xinhua) -- A medical source said 16 soldiers of Libya's eastern-based army were killed and 20 others were injured in Thursday's battle after which the army reseized two oil ports from a rival militia group.

"The emergency department received 16 dead and more than 20 injured today as a result of the clashes in the oil crescent region throughout the day," the source, from a hospital in the eastern Ajdabiya city, told Xinhua Thursday.

The source added that over 50 militants from the rival militia group were killed. "They are expected to be recovered by the Red Crescent teams in the coming hours," the source said.

Ajdabiya is less than 100 km away from the oil crescent region, where several key oil ports are located.

The eastern-based army, known as the Libyan National Army (LNA) and led by General Khalifa Haftar, announced Thursday that they had recaptured the oil ports of Ras Lanuf and Es Sidra.

Previously a military official under former leader Muammar Gaddafi, Haftar took control of most of the eastern part of Libya in the civil war. The LNA that he commands is opposed to the United Nations-backed government in Tripoli.

The Benghazi Defense Brigades militant group launched attacks on oil installations in the oil crescent region last week, resulting in clashes with the LNA.

Libya's state-owned National Oil Corporation (NOC) has evacuated all employees from the area. It said the conflict caused the loss of 240 thousand barrels of oil, and seems to have caused an "environmental disaster" due to damage to the oil tanks.

The UN Mission in Libya condemned the attack, saying "This dangerous escalation puts Libya's economy in jeopardy and risks igniting a widespread confrontation."