There are fears the Iranian proxy may attack shipping in the Red Sea, adding to global economic woes.
The Iran-backed group could bring a second crucial waterway to a standstill, writes Sebastian Usher.
Aid groups - a lifeline for millions of Yemenis - are being squeezed out of existence in areas under the control of the rebels, the BBC hears.
The Pakistani convict called himself a "walking dead person" just days before his last voyage destined for Houthi rebels in Yemen.
Israel's defence minister says he "died of wounds" sustained in an Israeli air strike in the Yemeni capital in late August.
The Israeli military says its "most powerful strike" in Yemen targeted security and military targets, but the Houthis say civilian facilities were hit.
The Israeli military says it hit military targets, but the Houthis say only civilian sites were targeted.
The food and children's agency workers are the latest UN staff detained by Houthi authorities.
Ahmed Ghaleb Nasser al-Rahawi and several other Houthi officials were killed in the attack, the Iran-backed movement says.
