At least 14 people have been killed and 25 wounded during clashes in eastern Libya between armed groups loyal to official government and Islamist groups, two medical sources said on Saturday.
The fighting, which was continuing on Saturday, erupted on Thursday in the town of Ajdabiya, the same day as Libya's warring factions signed a United Nations-brokered agreement to form a unity government. Western powers hope the deal will bring stability and help to combat a growing Islamic State presence.
However, the agreement faces questions from critics about how representative the proposed government will be, and whether armed factions on the ground will obey the new government. Some brand it a U.N.-imposed deal.
Casualties in the Ajdabiya fighting included civilians or members of groups supporting the Libyan National Army, said the sources who asked not to be named. They added that casualties from the other side were not treated in the town's hospitals.
It was unclear whether the Islamist fighters were affiliated to Islamic State militants.
In a separate incident, two guards were wounded when an unknown group attacked the military intelligence building in the western town of Sabratha, the mayor said.
Islamic State has exploited a growing security vacuum in Libya, where two administrations - each with its own government and parliament - are fighting for control four years after the toppling of Muammar Gaddafi.
The official prime minister and parliament have been based in the east since a rival group seized the capital Tripoli. Its government has been working from hotels in the city of Tobruk, about 270 km (167 miles) from Ajdabiya.
Both sides have several former anti-Gaddafi rebel groups fighting for them. After Gaddafi's ouster, the various factions split along political, regional and tribal lines.
Militants loyal to Islamic State, the group which has seized large parts of Syria and Iraq, have taken over the central city of Sirte, to the west of Ajdabiya.