TRIPOLI, June 14 (Xinhua) -- The UN Support Mission in Libya (UNSMIL) condemned Thursday the terrorist attack on Libyan oil crescent region.

"UNSMIL condemns the attack on the Libyan oil ports of Ras Lanuf and Es Sider on Thursday. This dangerous escalation in Oil Crescent area puts Libya's economy in jeopardy and risks igniting a widespread confrontation," said the mission.

"Calm must be restored immediately. The unity of Libya must come first," the mission added.

Totally five Libyan army soldiers were killed when a terrorist group called Benghazi Defense Brigades, allied with Ibrahim Jathran, a wanted ex-chief of oil installation guards, launched an attack earlier on Thursday and clashed with the army forces there.

The attack led to a loss of 240 thousand barrels of oil, and all government employees were evacuated, according to the state-owned National Oil Corporation.

The oil crescent region is located some 500 km east of the capital Tripoli, which contains the country's largest oil ports.

The army's information department earlier said that "Benghazi Defense Brigades tried to penetrate into the oil crescent region and ignite an oil reservoir in Veba oil field of al-Harouge oil company."

The army forces defeated and expelled the militants. The air force targeted those fleeing.

In a televised statement, Jathran confirmed that the attack is a "battle to lift the injustice of the people of the oil crescent, not for a personal, tribal, regional, or partisan purpose."

On September 2016, the army took control of the oil crescent region and expelled Jathran's forces, who closed major oil ports, making the country lose billions of U.S. dollars.

The UN-backed Libyan prime minister, Fayez Serraj, condemned the terrorist attack, calling it an "irresponsible escalation pushes the country into civil war that the Libyan strive to avoid."