TRIPOLI - Fighting between powerful militias battling for control of Tripoli’s airport broke out again on Friday, just hours after they had agreed a truce, witnesses said.The clashes came as the government sought United Nations help to prevent the country from becoming a “failed state”.Gunfire and blasts were heard in Tripoli’s Abu Slim neighbourhood, some 15 kilometres (nine miles) south of the airport, an AFP correspondent said. Residents said the battles pitched rival militias against each other.The airport has been closed since Sunday, when the gunmen from the city of Misrata launched an attack on the facility, which has for the past three years been held by liberal, anti-Islamist fighters from Zintan, southwest of the capital. Foreign Minister Mohamed Abdelaziz has asked the UN Security Council to dispatch experts to train Libya’s defence and police forces to ensure they can protect oilfields, airports and other vital sites.The call came in the wake of the airport attacks and amid a surge of violence across the country, with clashes between rival militias sparking fears of all-out civil war.Tripoli’s mayor and leaders of battling militias said overnight that a truce had been agreed and that control of the international airport would be handed over to neutral forces.Mokhtar Lakhdar, a commander for the Zintan forces, told AFP that a truce had been agreed under the authority of the city’s governing council. Since Sunday, dozens of rockets have been fired at the airport, badly damaging aircraft and the main terminal building.Ex-rebel fighters from Zintan and Misrata, east of Tripoli, both played a key role in the NATO-backed uprising that toppled dictator Moamer Kadhafi in 2011. But they have become fierce rivals in the deadly power struggle between armed groups that followed and which is now wracking the North African country.Ahmed Hadeia, a spokesman for the rival Misrata fighters, said the ceasefire was “only around the airport” and did not include other sites controlled by the Zintan forces.Misrata leaders said in a statement read out Thursday on television that the fighting at the airport was a “battle of revolutionaries... against followers of the old regime” of Kadhafi.The clashes revived fears of the conflict spreading inside Tripoli itself, with official results still awaited from a June 25 election to the parliament previously dominated by Islamists.“Should Libya become a failed state, kidnapped by radical groups and warlords, the consequences would be far-reaching and perhaps beyond control,” Abdelaziz warned the Security Council as he requested UN help.“We are not asking for military intervention,” he said. “We are asking for a team from the UN specialised in the field of security.”Libya could become a “hub for attracting extremists”, feeding radicalism and the arms flow in the region and further afield in Syria, said Abdelaziz.“Don’t you think that such patterns that are indicative of heading toward a failed state would justify a stronger, more strategic engagement from the Security Council?”In a statement, the 15-member Security Council said it condemned the recent violence in Libya and said it made “it even more difficult for the Libyan authorities to govern effectively”.The Council would ask UN Secretary General Ban Ki-moon to examine the Libyan request for aid and present “options”, said Eugene-Richard Gasana, the Rwandan chair of the UN body.Last week, the United Nations evacuated its staff from Libya after the latest upsurge in fighting.Abdelaziz said a new UN mission to help train the security forces would ensure Tripoli keeps control of vital oil revenue after militant groups seized oil terminals last year.The blockades of the oil facilities, that finally came to an end this month, deprived Libya of more than $30 billion in revenue over 11 months, the foreign minister said.