The United States said Saturday it was looking into reports that American anti-tank missiles were found by forces loyal to Libya's unity government at a captured rebel base.
The New York Times reported Friday that four Javelin missiles were found at a base used by men under the command of Khalifa Haftar, a military leader who has waged a months-long offensive against Libya's internationally recognized government based in Tripoli.
Markings indicate the missiles were first sold to the United Arab Emirates, a major buyer of US arms.
"We take all allegations of misuse of US origin defense articles very seriously. We are aware of these reports and are seeking additional information," a State Department spokesperson said on condition of anonymity.
"We expect all recipients of US origin defense equipment to abide by their end-use obligations."
The missiles were apparently discovered this week when forces loyal to the Government of National Accord (GNA) recaptured the strategic town of Gharyan in a surprise attack, seizing the main supply base for Haftar's offensive.
In Tripoli, the GNA on Saturday showed journalists three Javelin missiles and seven Chinese-made Norinco GP6 artillery weapons it said had been seized from Haftar's base.
"These are a sample that we have obtained permission to bring here," GNA fighter Ibrahim al-Touil said, adding he could not disclose the total number of the weapons.
The New York Times reported that markings on the missiles indicated they had been sold to the UAE, a US ally, in 2008.
If they were then sold or transferred to Haftar, that would violate both the terms of the sale and a UN arms embargo on Libya, the report said.
The UAE, Egypt and Saudi Arabia are seen as key supporters of Haftar.
Chinese-made attack drones were also found, the newspaper reported.
The State Department official said Washington supports the efforts of UN special envoy to Libya Ghassan Salame "to help avoid further escalation and chart a path forward that provides security and prosperity for all Libyans."
"We call on all parties to rapidly return to UN political mediation, the success of which depends upon a ceasefire in and around Tripoli," the US official said.
Hundreds of people have been killed and tens of thousands displaced in the offensive on Tripoli, while diplomatic efforts to revive political talks have foundered.