Yemen’s Houthi rebels have launched more than 150 ballistic missile attacks against Saudi Arabia since the start of the year, a top US commander told the US Congress this week. The kingdom has faced a barrage of attacks on its capital, Riyadh, and cities that are close to its borders with Yemen. The Saudi Air Force intercepts the majority of assaults. “Since the start of the year, Iranian-aided Houthi forces have launched more than 150 ballistic missiles, [cruise missile], and [drone] attacks against military, infrastructure, and civilian targets in Saudi Arabia,” commander of US forces in the Middle East, Marine Gen. Frank McKenzie, said late on Tuesday. General McKenzie, who is in charge of American forces in the Middle East, said Iran’s support of the rebels will fuel the war in Yemen and increase regional tensions. "The Iranian regime’s provisioning of lethal aid to the Houthis to enable such attacks prolongs the conflict in Yemen, exacerbates regional tensions, threatens the security of Saudi Arabia, and extends the suffering of the Yemeni people who are subject to widespread food and water shortages, malnutrition, and insufficient healthcare services," he said. The top US commander warned that Iran's use of small or medium size drones for surveillance and attacks means that “for the first time since the Korean War, we are operating without complete air superiority." “Until we are able to develop and field a networked capability to detect and defeat UAS, the advantage will remain with the attacker,” he said, using an acronym for unmanned aerial systems. Elisabeth Kendal, a Yemen expert at Oxford University’s Pembroke college, said the rebels have attacked Saudi Arabia with drone and missile attacks more than 900 times. “Drones and missile attacks on Saudi Arabia by Yemen’s Houthis have become too frequent to report (over 900 so far),” she said on Twitter. Ms Kendal’s comments came as a university near the kingdom’s border with Yemen caught fire last Thursday after Saudi air defences intercepted a barrage of ballistic missiles and bomb-laden drones. The interception scattered debris on Jizan University’s campus, which caused a fire that has been contained, the Saudi-led coalition fighting the rebels said in a statement. There were no deaths or injuries, the statement said. Saudi Arabia blamed the Iran-backed rebels for the attack, saying the five ballistic missiles and four bomb-laden drones specifically targeted civilian areas and had been launched from the rebels’ stronghold of Saada in Yemen. Yemen has been mired in conflict since the Houthis ousted the internationally recognised government in the capital, Sanaa, in late 2014.