TRIPOLI - Several countries backing rival factions in Libya have violated an arms embargo which they had agreed to uphold a week ago at a summit in Berlin, the United Nations said on Saturday.Last Sunday, foreign powers backing opposing camps fighting over Libya's capital Tripoli agreed at a summit hosted by Germany and the United Nations to push the parties to a lasting ceasefire and respect an existing U.N. arm embargo."Over the last ten days, numerous cargo and other flights have been observed landing at Libyan airports in the western and eastern parts of the country providing the parties with advanced weapons, armored vehicles, advisers and fighters," the U.N mission to Libya (UNSMIL) said in a statement."The mission condemns these ongoing violations, which risk plunging the country into a renewed and intensified round of fighting," UNSMIL said.It blamed several countries which were present at the Berlin conference, without naming them.The United Arab Emirates and Egypt support eastern forces of Khalifa Haftar which have been trying to take Tripoli in a near-ten month campaign. The internationally recognized administration based in Tripoli trying to fend off Haftar's forces is backed by Turkey.Fighting had abated in the past two weeks but on Saturday heavy artillery could be heard in Tripoli, a Reuters reporter said.The Berlin summit had gathered top officials from the UAE, Egypt, Turkey as well as western countries such as the United States, France, Britain and European Union.Germany also invited Haftar and Tripoli Prime Minister Fayez al-Serraj, who both met separately with Chancellor Angela Merkel but refused to sit down together.Libya has been engulfed in chaos since the toppling of Muammar Gaddafi in a NATO-backed uprising in 2011. Haftar is backing a rival administration based in the east.