US President Donald Trump said he ordered a series of airstrikes on the Houthi-held areas in Yemen on Saturday, promising to use “overwhelming lethal force” until Iranian-backed Houthi rebels cease their attacks on shipping along a vital maritime corridor. The Houthis said at least 18 civilians were killed. “Our brave Warfighters are right now carrying out aerial attacks on the terrorists’ bases, leaders, and missile defenses to protect American shipping, air, and naval assets, and to restore Navigational Freedom,” Trump said in a social media post. “No terrorist force will stop American commercial and naval vessels from freely sailing the Waterways of the World.”

Trump also warned Iran to stop supporting the rebel group, promising to hold the country “fully accountable” for the actions of its proxy. This comes two weeks after the US leader sent a letter to Iranian leaders offering a path to restarting bilateral talks between the countries on Iran’s advancing nuclear weapons programme. Trump has said he will not allow it to become operational. Houthis reported explosions in their territory on Saturday evening, in Sanaa and the northern province of Saada, the rebels’ stronghold on the border with Saudi Arabia.