Dubai – U.S. President Donald Trump promised “major military punishment” for Iran and its Houthi allies on Thursday after the Yemeni fighters struck two Saudi oil tankers in the Red Sea, extending the Middle East war to a second major shipping chokepoint.

Fears that disruption could widen further to block another sea route sent global oil prices surging in one of the steepest rises of the war. Brent crude rose more than 6%, breaking through $100 a barrel for the first time since May.

Two weeks since the effective collapse of an interim truce meant to end the war, the U.S. military launched airstrikes on Iran overnight into Thursday, prompting Iran to fire at neighboring Arab countries that host U.S. bases. The U.S. military fired another round of missiles at Iran late Thursday and early Friday in the 13th consecutive night of attacks.