The military commander of eastern Libyan forces said on Saturday that they would continue fighting militias allied to the Government of National Accord in Tripoli.
Field Marshal Khalifa Haftar, commander of Libyan National Army, has been waging a campaign for more than a year to capture the capital from the militias used by the GNA to defend it.
The military tide has been reversed in recent weeks, and his forces lost several towns and a key airbase.
Field Marshal Haftar's side controls the country’s east and most of the south, while the GNA controls areas in the west, including Tripoli.
In a two-minute audio speech addressed to his forces, he said they “will fight and fight” against “Turkish colonialism”.
Turkey is aiding the embattled government in Tripoli. It has recently stepped up its military support with armoured drones, air defences and Syrian mercenaries with links to extremist groups.
“To our brave officers and soldiers, you are fighting a holy war that is open to all fronts, a comprehensive war in which there is nothing but victory,” Field Marshal Haftar said in the speech.
“Every Turkish solider, mercenary sent by [Turkey's President Recep Tayyip Erdogan] to Libya and every traitor who has allowed the occupier to return is a target of our armed forces.”
US President Donald Trump called for a "rapid de-escalation" of the Libyan conflict on a call with Mr Erdogan on Saturday, the White House said, after recent gains by forces backed by Turkey prompted threats of retaliation.
Ankara said the Nato allies agreed to continue pursuing stability in the eastern Mediterranean region, including in Syria, while a spokesman for Mr Erdogan said the international community must stand with Turkey in the Libyan conflict.
Col. Mohamed Gnounou, a spokesman for the Tripoli-allied forces, said on Saturday that they seized two military camps on the outskirts of Tripoli that LNA forces captured at the start of their campaign last year.
Field Marshal Haftar's side said its fighters were merely completing a retreat of 2 to 3 kilometres from Tripoli’s southern reaches to allow families to visit each other safely in celebration of the Eid al Fitr holiday Sunday.
It also said they had retaken the Yarmouk military camp and killed “large number of the militias" and captured a dozen others.
It said they shot down two Turkish drones over southern Tripoli, which were attacking their forces.
The claims of the two sides could not be independently verified.
The US ambassador to Libya, Richard Norland, called Saturday for a halt to the “destabilising flow” of foreign military equipment and mercenaries into Libya.
Aguila Saleh, the Speaker of Libya's eastern Parliament, called for the UN Security Council to withdraw its recognition of the Tripoli government and appoint a new administration representing all Libyan regions.
In an address aimed at the Libyan people on the eve of Eid Al Fitr, Mr Saleh called for Tripoli to be cleared of “terrorist groups” and a fair distribution of the nation's oil and gas revenues.
The escalation in fighting comes despite increased international pressure on both sides to return to negotiating a political settlement and to halt the violence over concerns about the spread of the coronavirus.
Libya has reported at least 75 cases of Covid-19, the illness caused by the virus, including three deaths.