"The IS attacked Al-Fag'ha gate in Al-Jufra this morning, slaughtering nine soldiers and two civilians," said spokesman Ahmad al-Mesmari, Xinhua reported.
The checkpoint was located some 500 km south of the capital Tripoli, he added.
The army has been engaged in a violent war against extremist groups in eastern Libya for more than three years.
Earlier in July, the army said it had taken control of Benghazi, the second largest city in Libya.
Last December, forces allied with the UN-backed government of national accord in Tripoli freed Sirte, a city some 450 km east of Tripoli, after nearly seven months of fighting against the IS.
However, the IS remnants remain present in parts of Libya despite defeats.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
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