Staff have been evacuated from three oil fields in eastern Libya because of fears of attacks by Islamic State militants, but production has not been affected because the fields are shut, oil and security officials said on Sunday.
Islamic State militants have launched frequent attacks on Libyan oil fields and terminals in recent months, damaging facilities but not taking control of them.
Unlike in Syria and Iraq, Islamist militants have never controlled oil fields in Libya, but officials worry this could happen in the future, along with existing material and human damage.
Mohamed al-Manfi, an oil official based in eastern Libya, said the Wafa field had been completely evacuated and the Tibesti and Bayda fields were partially evacuated after security forces warned of possible planned attacks.
A security source said told Reuters that fighters loyal to Islamic State had been mobilizing in Nawfiliyah, a town between the extremist group's Libyan stronghold of Sirte and the oil ports of Es Sider and Ras Lanuf.
Earlier this month five members of the Petroleum Facilities Guard were killed in an attack by suspected Islamic State militants near Bayda field, about 250 km (155 miles) south of Es Sider and Ras Lanuf. The guard is a semi-military force that controls many oil facilities in the east.
Labour disputes, militant attacks and conflict between local communities and armed factions have sharply cut back Libya's oil production in recent years.
Production currently stands at less than one fifth of the 1.6 million barrels per day the OPEC member was producing before the 2011 uprising that toppled Muammar Gaddafi.