Yemen’s Houthis said they attacked “sensitive” sites in the Saudi capital Riyadh on Saturday with missiles and drones, hours after flames and a large plume of smoke were seen near the city’s main airport.Saudi Arabia had sent alerts overnight warning of potential danger around Riyadh, amid an escalation in attacks by the Houthis in the kingdom.Reuters video and photographs showed a huge pillar of black smoke rising in the area, with the airport highway, main terminal building and other...