Houthi rebels in Yemen have employed an unmanned submarine for the first time since attacks in the Red Sea and Gulf of Aden began, ABC News reported.
The unmanned underwater vessel (UUV), which gives the Houthis advanced capability and a shifting strategy, likely was supplied by Iran, according to a former Defense Department official and CIA agent.
"The Houthis are not likely capable of manufacturing these weapons on their own, so they are probably coming from Iran," ABC News national security and defense analyst Mick Mulroy said.
"The Houthis and the IRGC [Islamic Revolutionary Guard Corps] are adjusting their strategy, apparently because they haven't been successful in striking a U.S. naval vessel," Mulroy added.
"If one or more of these weapons get through and kill U.S. sailors, Iran should expect to be held directly responsible."
In response to the rebels' use of the UUV, the U.S. conducted self-defense strikes on five targets in the Houthi-controlled area of Yemen.
"Unmanned surface and subsurface vessels are likely more difficult to detect and destroy than aerial drones and anti-ship missiles," Mulroy said, ABC News reported Monday night.
The U.S. Coast Guard said it intercepted a cache of weapons — including components for the unmanned vessels — aboard a ship heading from Iran to Houthi-controlled Yemen on Jan. 15, the U.S. said, ABC News reported.
The Houthis have been attacking ships and assaulting shipping through the crucial Red Sea corridor — the Bab el-Mandeb Strait — in the wake of Israel's attack on Gaza following the Hamas terrorists' Oct. 7 massacre.
This past week, the rebels seriously damaged a ship in a crucial strait and apparently downed an American drone worth tens of millions of dollars.
On Monday, both the Houthis and Western officials acknowledged one of the most serious attacks on shipping launched by the rebels. The Houthis targeted the Belize-flagged bulk carrier Rubymar with two anti-ship ballistic missiles, one of which struck the vessel, the U.S. military's Central Command said.
The Houthis have targeted American ships to no avail.
Mulroy said a UUV could "overwhelm the ship's defenses" by attacking from multiple dimensions, a so-called "swarm attack."
The U.S. military said it hit a UUV Sunday and also struck an unmanned vessel that moves on the surface, ABC News reported.
The U.S. has been increasing defensive strikes since another militia group, also backed by Iran, struck the U.S. base in Jordan and killed three service members.
The Associated Press contributed to this story.