BENGHAZI, Libya (Reuters) - Islamic State militants clashed with a Libyan force guarding oil ports near Brega terminal on Saturday, killing one guard and wounding four including Ibrahim Jathran, leader of the Petroleum Facilities Guard (PFG), a spokesman and medical sources said.

Libyan militia leader Ibrahim al-Jathran, head of an autonomy movement in Cyrenaica province, speaks during an interview with Reuters in Brega October 20, 2013. REUTERS/Esam Omran al-Fetori

Islamic State has a base in the Libyan city of Sirte and has launched frequent attacks against oil facilities and ports, including major export terminals that are closed but controlled by Jathran’s PFG brigades.

The PFG is one semi-official armed group that is backing a new unity government in Libya, where two rival administrations and their loose alliances of former rebels have been battling for control after the 2011 fall of Muammar Gaddafi.

Fighting between PFG and a convoy of Islamic State militants broke out 52 km south of the Brega oil terminal early on Saturday, PFG spokesman Ali al-Hassi and a medical source said.

Hassi said those wounded included Jathran, though he did not give details of how Jathran was injured.

He said the clashes had begun early on Saturday when guards spotted a convoy of about 100 vehicles, which they engaged in fighting for several hours. A number of Islamic State fighters had been killed and six vehicles seized.

The convoy had come from the eastern city of Derna, Hassi said. Islamic State fighters retreated from long-held positions around Derna this week.

Eastern military forces have entered al-Fatayeh, an area south of Derna from which Islamic State withdrew, but troops and civilians have suffered heavy casualties from mines and booby traps. More than 30 people have been killed and 11 wounded in such incidents over the past four days, military spokesman Abulkarim Sabra said on Saturday.

The new U.N.-backed unity government is trying to establish its authority over Libya, where a self-declared Tripoli government and a rival in the east and various armed factions have been vying for power and a share of the country’s oil wealth for two years.

Islamic State’s rise in Libya worries Western governments who are offering military and financial aid to the new unity government. But the new administration is still establishing itself in Tripoli and faces resistance from hardliners who reject its authority.