A suicide attack on Wednesday targeting Libyan Army troops in the eastern Libyan city of Benghazi killed at least 15 soldiers.
The medical sources said in Tripoli that the attack struck a gathering of Libyan Army forces loyal to General Khalifa Haftar near Quarsah district, in the north-western suburbs of Benghazi.
The sources also said at least 16 soldiers were wounded in the attack.
It said that no group has immediately claimed responsibility for the attack, but similar violence has been claimed by Islamic State terrorists.
It said that the movement has taken advantage of chaos in Libya to seize territory along the sparsely populated central coast.
Libya has been in turmoil since the 2011 revolt that toppled long-time dictator, Moammer Gaddafi.
In March, a UN-backed unity government arrived in Tripoli, amid international hopes to re-establish stability.
However, Tobruk’s powerful military chief, Haftar, and a supportive parliament based in the city are still holding out against the nascent unity government.