The Saudi-led coalition fighting Yemen's Houthi rebels said it launched air strikes on military targets in the country's capital, Sanaa, on Saturday morning. The coalition urged civilians to stay away from the targeted areas, Saudi state-run television reported. The sites were not identified. The coalition has ramped up strikes on rebel sites in Sanaa in recent days amid heavy fighting around the city of Marib, the government's last stronghold in northern Yemen. The Iranian-backed Houthis have held Yemen’s capital since September 2014. Although the intervention of the Saudi-led coalition halted their march south in 2015, the war has slogged on for years and created the world’s worst humanitarian crisis. The Houthis have repeatedly launched cross-border attacks on Saudi Arabia using drones and missiles.