A United States Navy submarine torpedoed and sank an Iranian warship in the Indian Ocean, US Defense Secretary Pete Hegseth confirmed Wednesday, describing the strike as a demonstration of America’s global military reach amid escalating conflict with Tehran.

Speaking at a Pentagon news conference, Hegseth said the Iranian frigate believed it was operating safely in international waters before being struck. “An American submarine sunk an Iranian warship that thought it was safe in international waters. Instead, it was sunk by a torpedo,” he said, characterizing the attack as a “quiet death.”

General Dan Caine, a senior US military official, said the operation marked the first time since World War II that a US submarine had sunk an enemy ship. He added that more than 20 Iranian naval vessels have been destroyed since the outbreak of hostilities, effectively neutralizing what he described as Iran’s major naval presence in the theater.

Sri Lankan authorities confirmed that the frigate, identified as IRIS Dena, sank just outside the island nation’s territorial waters, roughly 40 kilometers south of the port city of Galle. The vessel reportedly issued a distress call at dawn, and Sri Lankan naval units reached the site within an hour.

Foreign Minister Vijitha Herath told Parliament that 32 critically wounded sailors were rescued and transferred to a hospital in southern Sri Lanka. However, 148 crew members remain missing, and hopes of further survivors are fading. Sri Lankan navy spokesperson Buddhika Sampath said search and rescue efforts are ongoing under international maritime obligations.

When rescue teams arrived, the ship had already sunk, leaving behind debris and an oil slick, officials said.

The sinking comes amid an intensifying US-Israeli campaign against Iran, with Washington stating that one of its key objectives is to dismantle Iran’s naval capabilities. Sri Lanka, which has maintained neutrality in the broader conflict, has urged dialogue while ensuring compliance with its international search-and-rescue responsibilities.

Security was tightened around the Galle hospital as injured sailors were brought ashore. Iran’s embassy in Colombo has yet to issue an official statement.

The incident significantly expands the maritime dimension of the conflict, raising fresh concerns over security in key Indian Ocean shipping lanes.