Rescuers pulled six crew members alive from the Red Sea after Houthi militants attacked and sank a second ship this week, while the fate of another 15 was unknown after the Iran-aligned group said they held some of the seafarers.

At least three of the 25 people on board the Eternity C were killed after it was attacked by the Iran-backed group.

Israel’s military launched airstrikes early Monday targeting ports and facilities held by Yemen’s Houthi rebels, with the rebels responding with missile fire targeting Israel

The U.S. military spent hundreds of millions of dollars earlier this year in a six-week barrage intended to stop the Iran-backed Houthi rebels in Yemen from targeting ships in the Red Sea.