Yemen’s Houthi rebels have warned shippers that “any Israeli vessel” traveling through nearby Mideast waters is now a target as Israel continues to block aid to the Gaza Strip.

The warning from the Houthis again throws into chaos a crucial maritime waterway between Asia and Europe, threatens revenue from Egypt’s Suez Canal and possibly will halt aid shipments to war zones. The rebels in the past have also had a loose definition of what constitutes an Israeli ship, meaning other vessels could be targeted as well.