At least 11 people were beheaded on Wednesday in an attack by Islamist fighters on a checkpoint controlled by forces loyal to military commander Khalifa Haftar in central Libya, according to a spokesman for Haftar's self-styled Libyan National Army.

Nine soldiers and two civilians were among those "slaughtered" at the checkpoint, Colonel Ahmad al-Masmari said in a tweet, blaming Islamic State.

Both Islamic State and Benghazi Defense Brigades, another Islamist militia opposed to Haftar, have fighters in the Jufra region where the attack took place, some 310 miles south of the coastal city of Sirte.

Haftar is aligned with a government based in the east of Libya, which is vying for power with the United Nations-backed unity administration of Fayez al-Sarraj in the capital, Tripoli. Haftar's forces now control most of eastern Libya, including key oil facilities.

The North African oil exporter slipped into chaos after long-time leader Moammar Gadhafi was killed in a 2011 revolt. Islamic State and other radical Islamist groups exploited the ensuing lawlessness to gain a foothold in Sirte but were driven out by fighters loyal to the Tripoli government following lengthy battles last year.