Two weeks after the collapse of an interim truce meant to end the war, the Iranian armed forces responded by firing at US bases in neighbouring Arab countries and warning people there that they may strike non-military buildings used by US personnel.
The Houthis, who control northern and western Yemen, have announced a naval blockade on Saudi Arabia, which has diverted millions of barrels of oil each day by pipeline to the Red Sea to skirt Iran's near-total blockade of the Strait of Hormuz.
The entrance to the Gulf has so far been the focus of a war that has killed thousands in almost five months, stoked global inflation and fanned fears of an economic downturn.
The Houthi fighters struck two Saudi tankers on Thursday in the Red Sea's Bab el-Mandeb strait, boosting oil prices seven per cent to top $US100 ($A143) per barrel for the first time since May.
Sources said Pakistan was exploring a path towards a resumption of stalled talks between the US and Iran over ending the war, following a push initiated by China.
Exploratory discussions took place during a visit by Iran's Interior Minister Eskandar Momeni to Islamabad this week - his second within the last 10 days, three Pakistani sources said. All three sources cautioned that the obstacles to any talks with the US remained high.
Meanwhile, the Houthi attacks forced several other tankers to turn around and head north through the Suez Canal, potentially using a much longer route to reach Asia by sailing around Africa.
Shipping insurance costs through the southern Red Sea doubled for some companies on Thursday, sources said. Still, half of the 18 ships exiting Bab el-Mandeb on Thursday were carrying crude oil, including two Chinese supertankers.
The number of tankers crossing through the Strait of Hormuz fell to just one on Thursday, the lowest since May 7.
The Iranian and Omani foreign ministers discussed security developments and maritime navigation in the Strait of Hormuz that runs between the two countries in a phone call, a statement on Iranian Foreign Minister Abbas Araqchi's Telegram channel said.
Trump said on social media that he would hold Iran accountable for any further attacks by Yemeni fighters, "and major military punishment will be inflicted upon Iran and, of course, the Houthis, themselves".
He told Axios he was considering re-launching major combat against Iran. "They haven't received enough pain yet," the US news outlet quoted him as saying.
In a statement on X, the Iranian health ministry said 59 people had been killed and 666 wounded since the resumption of clashes with US forces in late June. Iranian media cited the head of Iran's top joint military command as saying Iran would kill a member of the US forces for every Iranian killed.
The war has led to the deaths of 18 US service members. The Pentagon said on Monday that 100 service members had been injured since July 7 and 96 per cent have returned to duty.
The Iranian army said it had attacked US military equipment depots at Al-Adiri, officially named Camp Buehring, in northern Kuwait, and the positions of US troops at Camp Arifjan and at Camp Doha, near Kuwait City. In the early evening, Kuwait said its air defences were intercepting "hostile" targets launched from Iran.
