The so-called "Islamic State" attacks a Libyan oil terminal, the first case of its kind since the group seized the central coastal city of Sirte last summer. Libya's power vacuum has helped the militants make gains.
"Islamic State" (IS) militants on Monday launched an attack on the port of Siddra, Libya's largest oil terminal, military officials said.
Clashes between guards at the terminal and the militants led to the deaths of two guards and 10 of the attackers, Ali al-Hassi, spokesman for Libya's Petroleum Guards Force, said.
IS first carried out a suicide car bomb attack on a military checkpoint at the entrance to the town of Siddra, killing two soldiers, according to a colonel in the army loyal to the internationally-recognized government.
"We were attacked by a convoy of a dozen vehicles belonging to IS," Bashir Boudhfira said. "They then launched an attack on the town of Ras Lanouf via the south but did not manage to enter."
Another military official, also loyal to Libya's internationally-recognized government, based in Tobruk in the far east of the country, said the air force had intervened and rebuffed the attack.
IS seeks Libya's oil
Islamic State, which is based mainly in Syria and Iraq, controls an area of Libya's Mediterranean coast centered around the towns of Sirte and al-Nofaliyeh, west of Siddra.
IS has been trying to push east from Sirte for several weeks to reach the country's "oil crescent" where its main oil terminals such as Siddra and Ras Lanouf are based.
A Libyan oil official said a 420,000-barrel oil tank in Ras Lanouf caught fire during the clashes.
IS on Twitter claimed that its fighters had led an "attack on the Siddra area followed by violent clashes with the enemies of God."
The group said that the attack came after it took control of Ben Jawad town, 90 miles (145 kilometers) east of the central coastal city Sirte, which has been under IS control since June 2015.
Monday's attack was the first of its kind since IS seized the coastal city.
Its growing presence has lent urgency to international efforts to broker a peace deal between the Tobruk government and a rival, Islamist-leaning administration which controls the capital Tripoli.
Libyan politicians in December signed a UN-brokered agreement to set up a national unity government, but influential figures in both Tobruk and Tripoli are holding out against the deal.
Separately on Monday, a military plane that was targeting militant groups in the eastern Libyan city of Benghazi was shot down, though the pilot ejected, senior army commander Fadel al-Hass said.
bik/msh (dpa, AFP, Reuters)