Yemen's Iranian-backed Houthi movement has said its forces attacked two Saudi oil tankers in the Red Sea that had "violated" its blockade of Saudi ports, as the US carried out a 12th consecutive night of strikes on Iran. US President Donald Trump warned the Houthis on Thursday that if they did so again, the US would inflict "major military punishment" upon both them and Iran. Oil prices increased sharply following the latest developments in the region, with the cost of a barrel of Brent crude hitting $100.