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 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.
After the Houthis said they had struck two Saudi tankers on Thursday, Trump said he would hold Iran accountable for any further attacks by the fighters.
On Friday, several strikes hit Yemen's Hodeidah port, eyewitnesses said. The Saudi-led coalition in Yemen said it carried out a "proportionate military response operation" that targeted Houthi military sites in Hodeidah governorate.
The U.S. military launched air strikes on Iran late on Thursday and early on Friday, for a 13th consecutive night of attacks, prompting Iran to fire at neighbouring Arab countries that host U.S. bases.
U.S. missiles struck a Revolutionary Guards Navy headquarters in the Ziba Kenar area of the Caspian Sea province of Gilan, according to a security official in Gilan quoted by Iranian media. Provincial authorities said U.S. projectiles had also struck the port city of Bandar Anzali, according to the ILNA news agency.
Four people were killed and five injured in a U.S. attack on the Iranian city of Ahvaz, the state broadcaster IRIB said.
In a statement carried by Iran's Fars news agency, the Revolutionary Guards warned the populations of Gulf countries of potential strikes against U.S. military personnel who may be using "buildings in cities as locations to direct their crimes".
Trump told Axios on Thursday he was considering relaunching major combat against Iran. "They haven't received enough pain yet," the U.S. 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 U.S. 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 U.S. forces for every Iranian killed.
The war has killed 18 U.S. service members. The Pentagon said on Monday that 100 service members had been injured since July 7 and 96% have returned to duty. Officials have told Reuters that more than 500 U.S. troops have been injured so far.