Foreign Minister of the UN-backed Libyan government Mohamed Siala on Sunday demanded the United States to take a "clear and explicit stand" regarding the military campaign of the east-based army in and around capital Tripoli.

Siala's demand came after U.S. State Department spokesperson Morgan Ortagus expressed concern over the UN-backed Libyan government's requesting of military support.

Siala said that the Government of National Accord (GNA) is the sole and legitimate representative of the Libyan state, the foreign ministry said in a statement.

"The foreign minister demanded the U.S. government to take a clear and explicit stand regarding the aggression on the capital Tripoli, which he described as the main obstacle to the political track," the statement said.

The U.S. State Department on Saturday expressed concern over the UN-backed government requesting military support and the east-based army's threats to attack the city of Misurata, some 200 km east of Tripoli.

UN-backed Libyan Prime Minister Fayez Serraj on Thursday called on the United States, Britain, Italy, Algeria and Turkey to activate mutual security agreements.

Meanwhile on Sunday, Turkish President Tayyip Erdogan said Turkey will increase its military support to the internationally recognized government of Libya if necessary, after the two signed a military cooperation accord last month which Washington criticized as "unhelpful" and "provocative."

Turkey has said it could deploy troops to Libya if GNA makes such a request.

Speaking in the northern province of Kocaeli, Erdogan said Turkey had recently provided "very serious" support to the GNA, adding Libya was a country Turkey would support "with its life."

The east-based army has been leading a military campaign since early April in and around Tripoli, attempting to take over the city and topple the UN-backed government.

Thousands have been killed and injured in the fighting, and more than 120,000 were displaced by the violence.

(With input from agencies)