At least 11 people were beheaded Wednesday in an attack claimed by the Islamic State jihadist group on a checkpoint manned by forces of Libyan military strongman Khalifa Haftar.
Haftar's spokesman Colonel Ahmad al-Mesmari said "at least nine soldiers were beheaded... in addition to two civilians" when the jihadists attacked at dawn in the Al-Jufra region about 500 kilometres (300 miles) south of Tripoli.
IS group claimed responsibility for the attack via its Amaq propaganda channel on the Telegram messaging app, saying its fighters had killed or wounded "21 members of Haftar's militia".
Libya has been rocked by chaos since the 2011 fall and killing of longtime dictator Moamer Kadhafi in a NATO-backed revolution.
Jihadists, arms dealers and people traffickers have gained a foothold in the North African country as multiple authorities and dozens of militias vie for power.
Forces allied with the United Nations-backed Government of National Accord drove IS jihadists from their stronghold of Sirte on the Mediterranean coast in December.
The GNA underlined at the time that the battle against Islamist rebels was not over, as armed groups continue to hunt down IS group members who fled Sirte as the city fell.
Analysts and military sources say the group remains active in Libya, particularly in the desert south where the GNA holds little sway.
Haftar, who backs a rival administration that refuses to recognise the GNA, controls much of the country's vast southern desert.
His self-proclaimed Libyan National Army in May seized Tamenhant base near the southern city of Sebha after driving out a pro-GNA militia.
The following month, it seized Al-Jufra, including a key military air base, from the Benghazi Defence Brigades, a coalition that includes Islamists driven out of Libya's second city by pro-Haftar forces.
That placed the strongman in control of all the major cities and military bases in southern Libya.
Also in July, Haftar announced the "total liberation" of Benghazi, three years after his forces launched a military operation to seize the city.
But clashes have continued in the city, a bastion of the 2011 uprising that later fell to jihadists.
Forces loyal to Haftar regularly blame attacks against them on IS group, particularly in Benghazi.