The US vows to punish Iran after Houthi allies strike Saudi tankers, sending oil prices soaring and raising global alarm over escalating US Iran conflict.

In another escalation, the US president said American forces would broaden bombing to a nuclear site called Pickaxe Mountain, 220 kilometres south of Tehran.

The escalations intensify the risk of further pressure on global oil supply and prices.

Donald Trump threatened strikes on Houthis in the Red Sea.