Iran-aligned Houthi forces have seized Yemen's port city of Mocha and advanced towards strategic islands overlooking the Bab el-Mandeb Strait, as Iranian strikes have damaged US fighter aircraft at a base in Jordan, according to reports from Thursday.
The developments marked an escalation on two fronts of the Iran war, hours after US President Donald Trump said he expected the conflict to end after the US midterm elections.
Yemeni government military sources said the Houthis had gained further leverage over the Bab el-Mandeb Strait, one of the world's most important shipping routes, and had reached the Hanish Islands. If the Houthis gain control of the waterway, on the opposite side of the Arabian Peninsula from the Strait of Hormuz, it could give their backer Iran leverage over a second major transit corridor and further disrupt global energy supplies.
It could also complicate Trump's efforts to find an exit from a war that has hurt his Republican Party's electoral prospects ahead of the November midterms.
Yemen's Houthi-run humanitarian operations coordination centre said Red Sea navigation was safe for all shipping companies except Saudi vessels. Saudi Arabia, the world's largest oil exporter, has relied heavily on the Red Sea route since the Iran conflict effectively closed Hormuz, through which about one-fifth of global oil supplies previously flowed.
Yemeni government forces and their allies are relocating south along the Red Sea coast to Dhubab on the Bab el-Mandeb Strait, across from Perim Island, government military sources said. Control of Dhubab and the island is key to gaining hold of the strait.
UN Special Envoy for Yemen Hans Grundberg told the Security Council on Thursday that the international community must act to address "a new and more dangerous phase" in the Yemen war. The Houthis' capture of Mocha gave them "a direct presence on the approaches to one of the world's most vital straits", raising serious concerns about freedom of navigation, he said.
Nearly 50,000 people have fled the advance, with entire villages emptied and families trapped near frontline fighting with depleting food supplies, according to aid workers. Civilians in the Middle East's poorest country have found themselves victims of a global struggle for control over one of the most important shipping routes, which threatens to turn Yemen's on-off conflict into a forever war, The Guardian reported.
Jenifer Neidhart de Ortiz, the US representative at the UN Security Council, accused the Houthis of acting as "agents and tools of Iran". "This escalation is unacceptable, and those who enable it bear responsibility for its consequences," she said.
Yemeni government, Iranian and regional sources told Reuters the Houthi advance down the coast this week came with direct guidance from Iran's Revolutionary Guard Corps. Houthi spokesperson Mohammed Abdulsalam said, without elaborating, that the group's operations were defensive and would stop once attacks on Yemen stopped.
Brent crude rose as much as 4 per cent on Thursday to above $US105 a barrel as traders weighed the threat to another major shipping route.