The UN's special envoy to Libya on Monday urged a truce starting on Eid Al Adha, warning that foreign mercenaries were pushing the conflict beyond Tripoli and raising the chances of a full-scale civil war. In a harrowing briefing, Ghassan Salame called for the UN Security Council to support the release of 5,000 migrants from Libyan-run detention centres. At least 3,800 men, women and children held without charge are at risk of death from military attacks, he said, advising that his team had drawn up plans to free them. After almost four months of fighting near the capital, however, the conflict between the eastern-based Libyan National Army and the UN-backed rival Government of National Accord is widening. Hundreds of thousands of civilians have fled their homes and tens of thousands have crossed the border into Tunisia to seek safety, Mr Salame said, blaming both sides for a worsening situation that could provide a safe haven for extremists including ISIS. “The parties, ignoring calls for de-escalation, have intensified air campaigns, with precision air strikes by aircraft and armed drones,” he said. “There is increased recruitment and use of foreign mercenaries, alongside the use of heavy weapons and ground attacks.” A truce should be declared for Eid Al Adha, expected to begin around August 10, accompanied by confidence-building measures such as an exchange of prisoners between the LNA the GNA of Prime Minister Fayez Al Serraj, said the envoy. Almost 1,100 people including at least 106 civilians have been killed since LNA commander Field Marshal Khalifa Haftar began a surprise offensive on Tripoli in early April. Militias loyal to the GNA have since struck back, reclaiming territory lost early in fighting south of Tripoli. “More than ever, Libyans are now fighting the wars of other countries who appear content to fight to the last Libyan and to see the country entirely destroyed in order to settle their own scores,” Mr Salame said. Britain's permanent representative to the UN, Karen Pierce, called the briefing "grave and alarming". The death of 53 migrants in an air strike on the Tajoura Detention Centre near Tripoli on July 2 was one of the largest single-incident casualty tolls in years of fighting since the overthrow of longtime dictator Muammar Qaddafi in 2011. The deaths were all the more appalling because the UN support mission in Libya (UNSMIL) had shared the co-ordinates of the centre with the country's warring forces to prevent it from being attacked, the special envoy said. “To make matters worse, following UN-supported efforts by the UN to move the migrants to more secure locations, authorities in recent days have deposited 200 of them back into the bombed facility,” he told the council via video link from Tripoli. Of the Tajoura centre and others like it, Mr Salame added: “What is required is that they be shuttered. Towards this end, I urge the council to call upon the authorities in Tripoli to take the long-delayed but much-needed strategic decision to free those who are detained in these centres.” A reduction in violence remains the cornerstone of a return to the political process in Libya. The UAE, Britain, France and Germany are among world powers who have called for a ceasefire. The UAE has said it politically supports Field Marshal Haftar as the best possible long-term prospect for security and development in Libya. But the fighting is getting worse, said Mr Salame. Mitiga Airport, the only functioning airport in the Tripoli area, is under attack and civil aircraft are at risk of being hit. “I am afraid that with the almost daily bombardment luck will run out,” he said. With the GNA on June 26 having retaken Gharyan, the first city the LNA entered after starting its offensive, allegations of human rights abuses in the town are being investigated, according to the UN envoy. “The recent uptick in violence may worryingly presage a new phase in the military campaign but I do not judge that this will fundamentally alter the strategic stalemate,” Mr Salame said. “The parties believe they can achieve their objectives through military means. “The LNA maintains that they will not stop their attack until Tripoli is conquered while the GNA forces insist they can push General Haftar's forces back to eastern Libya.”