The first US strikes against Yemen's Houthis since Donald Trump took office killed 31 people, the rebels said on Sunday, with the US president warning "hell will rain down upon" the Iran-backed group if it did not stop attacking shipping.

The Houthis, who have attacked Israel and Red Sea shipping throughout the Gaza war, said children were among those killed.

Attacks on Sanaa, as well as on areas in Saada, Al-Bayda and Radaa, killed at least 31 people and wounded 101, "most of whom were children and women", Houthi health ministry spokesperson Anis Al-Asbahi said.

Footage on Houthi media showed children and a woman among those being treated in a hospital emergency room, including a dazed girl with blackened legs wrapped in bandages.

Trump, in a post on social media, vowed to "use overwhelming lethal force" to end the Houthi attacks, which the rebels say are in solidarity with Palestinians amid the Gaza war.

After halting their attacks when a ceasefire took effect in Gaza in January, the Houthis announced on Tuesday that they would resume them until Israel lifted its blockade of aid to the devastated Palestinian territory.

Late on Saturday, a plume of white smoke had risen over Sanaa after explosions rocked the northern district of the capital.

However, the Houthis sealed off areas around the blast sites, making it impossible to gauge the true scale of the destruction.

Mohammad Albasha, a US-based consultant, said the area targeted in Sanaa was home to senior Houthi leaders and considered their stronghold in the capital.

"This is the point of no return, and from now on, it's gloves off between the Houthis and CENTCOM," he said, referring to the regional US military command.

Amal, 29, who lives with her mother in Sanaa, said Saturday's attacks were "terrifying... windows were shattered and the walls of the house shook".

"Several military operations against the Houthis have been announced, but they've only added more casualties, most of them civilians."

"The homes and locations of the leaders are well-known, but the victims are always civilians." (AFP)