Yemen’s Houthi rebels on Sunday declared an escalation in their maritime campaign, announcing they will now target any ships belonging to companies that do business with Israeli ports, regardless of flag, ownership, or destination. The warning, delivered in a televised statement by the group’s military spokesperson, marks what the Iran-aligned militants described as the “fourth phase” of their operations against Israel.

“The Yemeni Armed Forces call on all countries, if they want to avoid this escalation, to pressure the enemy to halt its aggression and lift the blockade on the Gaza Strip,” the spokesperson said, calling the attacks a “religious, moral, and humanitarian responsibility.”

Houthi rebels launched their first campaign against merchant shipping of the year earlier this month, sinking two bulk carriers, killing at least four seafarers, wounding others, and kidnapping crew.