Haftar militia targeted by suicide bomber in eastern Libya
The militants targeted the eastern city of Ajdabiya, AFP reported, and it follows a wave of attacks from Islamic State group-linked militants against Haftar's self-styled Libyan National Army (LNA).
Meanwhile, militants stormed a checkpoint some 150 kilometres (90 miles) away and kidnapped one fighter manning the roadblock, a militia security source told the agency.
There was no immediate claim of responsibility for either of Tuesday's attacks.
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Haftar's forces have come under repeated attack from Islamic State group militants in recent months.
The fall of the group's former stronghold in Sirte has seen their fighters launch guerilla-style attacks on Haftar-linked militias in the east.
IS claimed responsibility for a car bomb attack in eastern Libya in March, which left at least three people dead.
Haftar-controlled Benghazi was also hit by twin bombings in January, killing at more than 20 people.
Libya has been torn between rival factions since the fall of long-time dictator Muammar Gaddafi in 2011, following a popular uprising.
Two rival governments formed - a UN-backed authority in the capital Tripoli and rival administration in the eastern city of Tobruk - and have fought for control of the country.
Haftar has backed the eastern authority.
The unrest has allowed radical militias to gain ground, with the IS-held city of Sirte falling to forces linked to the western authority in 2016.