A spokesman for Yemen's Houthis said on Thursday the group had attacked important targets in the Saudi Arabian capital Riyadh using four drones.The Iran-aligned Houthis have rejected a ceasefire proposal made last month by Riyadh because it did not include lifting an air and sea blockade imposed by a Saudi-led military coalition on the territories they control mainly in northern Yemen. Also, the Saudi-led military coalition said it destroyed a Houthi ballistic missile on its launchpad in Yemen, Saudi state TV reported, adding that the weapon was being prepared for launch toward the gas-rich of Yemeni province of Ma'rib.The Iran-aligned Houthis did not immediately confirm the claim.The conflict, seen in the region as a proxy war between Saudi Arabia and Iran, has caused what the United Nations says is the world's largest humanitarian crisis.