The Houthi militia has threatened a “strong and effective response” after the US carried out another strike in Yemen overnight,  ratcheting up tension as Washington vowed to protect shipping from attacks by the Iran-aligned movement.

The strikes increased concern about the escalation of a conflict that has spread through the Middle East since the Palestinian militant group Hamas and Israel went to war, with Iran’s allies also entering the fray from Lebanon, Syria and Iraq.

President Joe Biden said the US sent a private message to Iran about the Houthi attacks. He did not elaborate, telling reporters, “We delivered it privately and we’re confident we’re well prepared.”

The latest strike, which the US said hit a radar site, came a day after dozens of American and British strikes on Houthi facilities in Yemen.

“This new strike will have a firm, strong and effective response,” Houthi spokesperson Nasruldeen Amer told Al Jazeera. There were no injuries or “material” damage.

Mohammed Abdulsalam, another Houthi spokesperson, told Reuters the strikes, including the one overnight that hit a military base in Sanaa, had no significant effect on the group’s ability to stop Israel-affiliated vessels passing through the Red Sea and Arabian Sea.

The Pentagon said on Friday the US-British strikes had “good effects”.

Hans Grundberg, UN special envoy for Yemen, called on Saturday for maximum restraint by “all involved” and warned of an increasingly precarious situation in the region.

The Houthis say their maritime campaign is to support Palestinians under Israeli siege and attack in Gaza, ruled by the Iran-backed Hamas. Many of the vessels they attacked have no known connection to Israel.

The group, which controls Sanaa and much of the west and north of Yemen, has also fired drones and missiles up the Red Sea at Israel itself.

The guided missile destroyer Carney used Tomahawk missiles in the follow-on strike early on Saturday local time “to degrade the Houthis’ ability to attack maritime vessels, including commercial vessels,” US Central Command said in a statement on X.