The United States on Tuesday imposed sanctions on two commanders of Yemen's Houthi rebels, blaming them for civilian deaths and denouncing their ties with Iran as Washington seeks to halt the devastating war.

The Treasury Department said it would freeze any assets of the air force and naval commanders of the Houthis, who have defied international appeals by pursuing an offensive to seize the government's last northern stronghold.

With the rebels from the impoverished nation unlikely to have US bank accounts, the effects are largely symbolic but reinforce President Joe Biden's sharp criticism of Iran even as he opens the door to diplomacy and distances his administration from Saudi Arabia, which has been waging a devastating campaign to dislodge the Houthis.

"These individuals command forces that are worsening the humanitarian crisis in Yemen," said Andrea Gacki, the director of the Treasury Department's Office of Foreign Assets Control.

"The United States remains committed to promoting accountability of Houthi leadership for their actions, which have contributed to the extraordinary suffering of the Yemeni people," she said in a statement.

The Treasury Department said that both commanders had trained in Iran and acquired weapons from the clerical state, which has religious affinities with the Houthis and a shared hostility toward Saudi Arabia.

The Houthi naval commander, Mansur al-Saadi, masterminded deadly attacks against international shipping in the Red Sea and put fishermen and other civilians at risk with naval mines, the Treasury Department said.

The air force commander, Ahmad Ali Ahsan Al Hamzi, has carried out targeted drone strikes, it said.

The action comes after the Biden administration in one of its first acts rescinded a designation that the Houthis, formally known as Ansar Allah, are a terrorist organisation.

Aid groups said that the label put their work at risk as they had no choice but to deal with the Houthis, who effectively are Yemen’s governing authority in much of the country including the capital Sanaa.

The United Nations has called Yemen the world’s worst humanitarian crisis and voiced disappointment after a pledging conference Monday raised $1.7 billion in aid, far below the appeal of $3.85 billion.

A munition fired by Yemen’s Houthi rebels wounded five civilians in a border village in southern Saudi Arabia, state media reported on Tuesday, the kingdom’s latest casualties from cross-border fire.

The projectile slammed into a public road in the southern province of Jizan on Monday, wounding three Saudis and two Yemenis, Saudi civil defence was quoted as saying by the official SPA news agency.

Two homes, a grocery store and three vehicles were also damaged.

The US embassy in Riyadh condemned the cross-border fire, and called on the Houthis to "stop attacking innocent civilians and to engage in the diplomatic process to end this conflict”.

The rebels did not immediately claim responsibility.

The Iran-backed rebels have escalated attacks on the kingdom in recent weeks, while they step up an offensive to seize the Saudi-backed government’s last northern stronghold of Marib.

On Saturday, loud explosions shook the capital Riyadh as the Saudi-led coalition said it thwarted a Houthi missile attack, which sent shrapnel raining down on civilian homes.

No casualties were reported but at least one civilian home was damaged, state-run Al Ekhbariya television said.

Separately, the coalition said it intercepted six Houthi drones targeting the kingdom on Saturday, including the southern cities of Khamis Mushait and Jizan.