Suspected Islamic State militants attacked oil installations close to Libya's Ras Lanuf terminal today and the group threatened more attacks.
The engineer said two storage tanks from the Harouge Oil Operations company had been set on fire near Ras Lanuf, where militants also launched attacks earlier this month.
Islamic State fighter Abu Abdelrahman al-Liby said in a video posted on the group's official Telegram channel: "Today Es Sider port and Ras Lanuf and tomorrow the port of Brega and after the ports of Tobruk, Es Serir, Jallo, and al-Kufra."
The state-run National Oil Corporation (NOC) said the area was facing an "environmental catastrophe", with huge columns of smoke covering the area and damage to power lines supplying residential and industrial districts.
An energy official allied with Libya's eastern-based government, Mohamed al-Manfi, said a pipeline leading from the Amal oil field to the Es Sider terminal had been targeted. There were clashes between militants and Petroleum Facilities Guards, but Manfi and a guards source later said these had stopped and the militants had retreated.
Libya has become deeply divided since the fall of Muammar Gaddafi in 2011, with political and armed factions competing for power and for the country's oil wealth. Since the summer of 2014 it has two rival governments and parliaments, operating from the capital Tripoli and from the east.
Islamic State militants have taken advantage of the security vacuum to establish a foothold in the city of Sirte, which lies about 200 km (125 miles) along the coast to the west of Ras Lanuf and Es Sider.
OIL PRODUCTION DISRUPTED
The terminals, Libya's largest, have been closed since December 2014. The country's oil production is less than a quarter of its 2011 high of 1.6 million barrels per day.
Clashes between Petroleum Facilities Guards and Islamic State militants two weeks ago near Es Sider and Ras Lanuf left seven oil storage tanks damaged by fire and at least 18 guards dead.
The NOC sent a tanker to remove oil from the terminals in an effort to prevent further damage, but guards prevented it from loading, citing security concerns.
The NOC said on Thursday the "intransigence" of the guards had prevented it from avoiding further damage caused by the latest attack.