Several Libyan and regional media outlets had claimed in recent months that hundreds of Sudanese paramilitaries from the Rapid Support Forces (RSF) were deployed in Libya to fight alongside Haftar's Libyan Arab Armed Forces.
But a UN panel of experts on Sudan dismissed these claims in a report released on Monday.
"The panel has no credible evidence of the presence of Rapid Support Forces in Libya," the report said, AFP reported.
It said there were, however, many Arabs from Sudan's conflict-wracked region of Darfur and neighboring Chad fighting as "individual mercenaries" in Libya and they belonged to the same tribes that made up a majority of RSF personnel.
The UN experts' report also said several Darfuri armed groups operating in Libya "have participated in various clashes and military operations alongside Libyan warring parties".
Libya has been mired in chaos since a 2011 NATO-backed uprising that killed longtime dictator Muammar Gaddafi, with the main cleavage nowadays pitting Haftar's LAAF against a UN recognized government in Tripoli.
The deputy of Sudan's ruling transitional sovereign council, General Mohamed Hamdan Daglo, heads the feared RSF which has long been accused by human rights groups of committing widespread abuses in Sudan's Darfur provinces.
The report said Darfur itself did not see any large-scale outbreak of violence during the reporting period -- March to December 2019 -- although the region saw intercommunal skirmishes, militia attacks on civilians and tensions in major camps housing people displaced by the conflict.
It said that a main rebel group in Darfur, the Sudan Liberation Army-Abdul Wahid group, has strengthened its military capability after its revenues increased following the discovery of a gold mine in an area it controls.
"The movement has been able to strengthen its military capability by acquiring new weapons and ammunition from local militias and engaging in a recruitment drive," the report said.
The group fought Sudanese government forces for years during the regime of Omar al-Bashir, who was deposed during street protests in April last year.
The conflict in Darfur erupted in 2003, when non-Arab rebels took up arms against Bashir's Arab-dominated regime, whom they accused of marginalizing the region.
The conflict left at least 300,000 people dead and displaced 2.5 million others, the UN says.
The SLA-Abdul Wahid group has not participated in ongoing peace talks with Sudan's new transitional government which is negotiating with several other rebel groups in a bid to achieve a peace deal to end wars in Darfur as well as Blue Nile and South Kordofan states.