A suicide attack Tuesday against a checkpoint in eastern Libya killed at least two militiamen loyal to General Khalifa Haftar, a security source said.
The attack south of the city of Ajdabiya comes after the Islamic State group claimed a string of deadly assaults against roadblocks run by Haftar's Libyan National Army (LNA).
In another incident armed men also stormed another checkpoint some 150 kilometres (90 miles) away and kidnapped one of the militiamen deployed at the location, the militia security source said.
There was no immediate claim of responsibility for either of Tuesday's attacks.
Libya has been wracked by chaos since a 2011 uprising that toppled and killed its long-time dictator Moamer Kadhafi, with two rival authorities vying for control.
Haftar supports an administration based in the east of the country. A UN-backed unity government based in the capital has struggled to assert its authority outside the west.