TRIPOLI- The U.N. secretary-general appealed on Thursday for restraint from rival factions in Libya as forces from the east of the country moved to within 100 km (60 miles) of the capital Tripoli.U.N. Secretary-General Antonio Guterres, who arrived in Tripoli on Wednesday to promote peace talks, warned of the risk of serious fighting erupting.But skirmishes have already broken out as fighters from Khalifa Haftar's eastern-based Libyan National Army (LNA) move westwards. They clashed briefly on Wednesday with forces allied to Tripoli Prime Minister Fayez al-Serraj.By Thursday, LNA forces had reached a position south of Gharyan town, Mayor Gharyan Yousef al-Bdairi told Reuters by phone.The town, lying in the Western mountains about 100 km due south of the capital, is allied to the Tripoli government.The two sides fought skirmishes on Wednesday night but these had ceased, Mayor Bdairi said."The situation now is very calm inside the city. There is a gathering of those forces who came from the south," he said.Libya has been divided between the internationally recognized government in Tripoli and a parallel administration allied to Haftar since the overthrow of Muammar Gaddafi in 2011.The U.N.'s Gutteres said in a tweet he was deeply concerned by the military movements and the risk of confrontation."There is no military solution. Only intra-Libyan dialog can solve Libyan problems. I call for calm and restraint as I prepare to meet the Libyan leaders in the country," he said.The renewed confrontation was a setback for the United Nations and Western countries which have been trying to mediate between Serraj and Haftar, who met in Abu Dhabi last month to discuss a power-sharing deal.A national conference is set to follow this month to agree on a road map for elections.Libya is an oil producer and a hub for refugees and migrants trekking across the Sahara in the hope of reaching Europe.