By John Lee.
Forces loyal to Eastern-based commander Khalifa Haftar have seized oil ports in Libya's Oil Crescent.
The Petroleum Facilities Guards (PFG), headed by Ibrahim Jadhran, lost control of the ports of Es Sider (Sidra) and Ras Lanuf following an attack on Sunday. These ports together account for more than half of Libya's oil output.
Reports on Monday evening said that the ports of Zueitina, and possibly also Brega, had also fallen into Haftar's control.
The development throws further doubts on the viability of the Western-backed project to unite the country under a Government of National Accord (GNA).
The Presidential Council of the GNA said the "unjustified escalation will only prolong the conflict and will cause losses of Libyan lives and livelihood."
Read international reaction to the latest developments here.
(Sources: Reuters, Xinhua, BBC, AFP)