The US continued its "decisive and powerful" wave of air strikes on Houthi rebels targets on Sunday as part of efforts to stop Houthi attacks on shipping in the Red Sea.
Washington says some key Houthi figures are among the dead, but the rebels has not confirmed this.
Targets in the Al Jaouf and Hudaydah areas were hit early on Monday, according to the rebel’s, while the US Central Command said its forces had continued operations.
Updating an earlier death toll, Houthi sources posted on X that 53 people had been killed including "five children and two women", and that 98 people had been wounded.
US National Security Advisor Michael Waltz told ABC News that Saturday's strikes "targeted multiple Houthi leaders and took them out".
He told Fox News: "We just hit them with overwhelming force and put Iran on notice that enough is enough."
US Defence Secretary Pete Hegseth vowed an "unrelenting" missile campaign until the Houthi attacks stop.
"I want to be very clear, this campaign is about freedom of navigation and restoring deterrence," Hegseth said in a televised Fox Business interview.
The Houthis said it would continue to target Red Sea shipping until Israel lifted its blockade of Gaza, and that its forces would respond to the strikes.
The Houthis have claimed responsibility, without offering evidence, for two attacks on the US aircraft carrier USS Harry S. Truman and several American warships in the Red Sea, calling it retaliation for US strikes.
But a US official told Reuters news agency that US warplanes shot down 11 Houthi drones on Sunday, none of which came close to the Truman. The US is yet to respond to the second claim of such a strike.
UN Secretary-General Antonio Guterres on Sunday called for "utmost restraint and a cessation of all military activities" in Yemen.