A Libyan military prosecutor has ordered the arrest of General Khalifa Haftar and three other retired commanders, as reported by Anadolu Agency.
According to a statement by the military chief prosecutor's office, Haftar and three retired commanders were accused of commanding a Russian group that carried out kidnappings and murders in September.
Haftar's forces launched a campaign in April to capture Tripoli from Libya's internationally recognised Government of National Accord (GNA).
Clashes between the two sides since then have left more than 1,000 people dead and around 5,500 wounded, according to the World Health Organisation (WHO).
The oil-rich country has remained beset by turmoil since 2011, when longtime ruler Muammar Gaddafi was ousted and killed in a NATO-backed uprising after four decades in power.
Libya has since seen the emergence of two rival seats of power: one in eastern Libya, with which Haftar is affiliated, and the Tripoli-based GNA, which enjoys UN recognition.