The officials said today's blast at Nofaliya, 130 kilometers (81 miles) east of Sirte, also wounded two soldiers from the Libyan National Army.
The attack came just over a week after IS militants beheaded 11 people in an attack on a checkpoint in the central district of al-Jufra, some 300 kilometers (185 miles) south of Sirte, which IS held until Libyan forces expelled the militants late last year.
Bands of IS militants are believed to be roaming Libya's vast deserts around Sirte, preying on travelers and attacking isolated outposts belonging to the army or rival militias.