Saudi Arabia says it has shot down a drone launched into the kingdom by Yemen's Iranian-allied Houthi rebels. The Houthi drone attacks have picked up amid tensions between Iran and the U.S. in the Persian Gulf as Tehran's nuclear deal with world powers unravels. President Donald Trump says Iran still takes his threats seriously even after he decided against approving strikes in retaliation for Tehran's downing of a more than $100 million American surveillance drone over the Strait of Hormuz.