DUBAI, United Arab Emirates (AP) — In just days, Yemen’s Houthi rebels have begun a new, more violent campaign of attacks targeting ships in the Red Sea, sinking two of them and killing some of their crew.

The cost of insuring commercial ships that sail past Yemen’s Houthi militants surged after the rebels sank two ships and killed sailors this week, underscoring how the attacks have revived risk in the crucial waterway.

The attack on the Eternity C, which killed at least three of the crew, represents the most serious assault carried out by the Houthis in the crucial maritime trade route.