The Iran-backed Houthi rebels say they have closed the Bab el-Mandeb Strait, which sits on the southern end of the Red Sea and is a vital link for Saudi and international trade. Around 12% of the world’s trade, including a fourth of global container traffic, passes through the narrows. The rebels’ threat to blockade Saudi Arabia therefore has the potential to widen the Iran war and further disrupt global oil supplies and international trade. The Houthis said also on Thursday that they had attacked two Saudi oil tankers in the Red Sea, causing fires to break out on both. Saudi’s state-run news agency reported a fire on a tanker in the Red Sea following an attack, as did the United Kingdom Maritime Trade Operations Center. No casualties were reported.

Since the Iran war’s disruption of the Strait of Hormuz, the Bab el-Mandeb Strait has become more vital still to Saudi oil exports and to oil markets more broadly. The Houthis had said they would only stop vessels connected to Saudi Arabia or going in and out of its Red Sea ports. But during a similar blockade announced against Israel over the war in Gaza, the rebels attacked many vessels with little or no connection to that conflict. The threat alone could keep international shippers from using the route; supply chain difficulties could very well arise to a great extent in oil markets, but the effects may be more far-reaching.

Full report: A new threat by Yemen’s Houthis could widen the Iran war and put another trade chokepoint at risk.