The United States issued a Middle East security alert warning that unforeseen escalation could cause flight cancellations, airspace closures and rerouting near conflict zones after Yemen’s Iran-backed Houthis claimed missile and drone strikes on Riyadh and an oil facility in Yanbu. Iran warned of sustained retaliation against US bases and interests after any major new attack by Washington and its allies, while Brent crude rose 81 cents, or 0.78%, to $104.68 a barrel and West Texas Intermediate gained 76 cents, or 0.76%, to $101.06. Gulf markets closed lower, Iran said most shipping would remain blocked through the Strait of Hormuz until the June interim ceasefire was implemented according to Tehran’s interpretation, and a prediction market priced a potential US invasion of Iran by the end of 2026 at 16.5% YES, up from 16%.