Clashes between the Libyan pro-government forces and the Islamic State have led to the death of at least 34 soldiers, all drawn from the UN-backed unity government.
The attacks came as the fighters were preparing for a final assault on the jihadist stronghold of Sirte.
100 others were wounded in the Tuesday clashes, described as one of the bloodiest days since forces loyal to the Tripoli-based government, launched an offensive to retake the city from ISIS.
Further west in the city of Garabulli, 29 people were killed and a dozen others wounded in an explosion at an arms depot, that occured after armed residents and militiamen clashed.
According to the unity government, fighting took place in several parts of Sirte, where jihadists are pinned down in pockets of the coastal city.
It also said that said the death toll had risen from 18 to 34, with the number of wounded increasing from 70 to 100.
Sources indicate that about 200 loyalist troops have lost their lives and hundreds wounded since the start of the offensive.
The fall of Sirte would be a major blow to IS which has faced a series of setbacks in Syria and Iraq where local forces and a US-led coalition are pressing an offensive against their positions.