At least 87 people were killed after a United States submarine reportedly torpedoed an Iranian naval warship in the Indian Ocean, according to reports citing international sources. The vessel, identified as the IRIS Dena, sank off the coast of Sri Lanka, triggering a large-scale search and rescue operation.
The IRIS Dena, a Moudge-class frigate of the Iranian Navy, had recently participated in the multinational naval exercise MILAN 2026 hosted in India. The warship had also taken part in the earlier 2024 edition of the same exercise before returning to its operational deployment.
While the United States has not officially confirmed the casualty figures, US Defence Secretary Pete Hegseth acknowledged that an American submarine carried out the strike. Speaking to reporters, he described the operation as a demonstration of Washington’s naval capabilities amid the ongoing conflict with Iran.
According to Hegseth, the Iranian frigate believed it was safe while sailing through international waters but was struck by a torpedo fired from a US submarine. He referred to the incident as a “quiet death,” noting that it marked the first time since World War II that a US submarine had sunk an enemy warship using a torpedo.
The US Department of War also released a short black-and-white video that appeared to show footage from a submarine periscope followed by a distant explosion. Military analysts say releasing such near real-time visuals of a submarine strike is extremely rare and highlights the evolving nature of modern warfare and information dissemination.
Defence experts believe the Iranian vessel may not have detected the submarine even when it was operating at periscope depth, indicating the advanced stealth and tracking capabilities of the American submarine involved. Some analysts have suggested that the US Navy may have been monitoring the IRIS Dena throughout its journey from Iran to India for the MILAN exercise, a common intelligence-gathering practice among naval forces.
Meanwhile, Sri Lankan authorities have launched a major rescue operation after the frigate went down near the island nation’s coast. According to Sri Lankan officials, 32 sailors have been rescued so far, while dozens remain missing.
Sri Lanka’s Foreign Minister Vijitha Herath informed Parliament that the distressed Iranian warship sent out a call for help at around 5:08 a.m. IST. Sri Lankan naval units responded quickly under international maritime rescue obligations, dispatching the first vessel by 6 a.m. and a second shortly after.
Rescued sailors were taken to a government hospital in Sri Lanka’s southern Galle district for medical treatment. Naval spokesperson Buddhika Sampath stated that the Iranian frigate had already sunk by the time rescuers arrived at the scene.
Officials said the ship had a personnel capacity of nearly 180 crew members, though around 140 sailors were believed to be on board during the incident. Authorities have recovered numerous bodies, while search teams continue to look for missing crew members in the surrounding waters.
The sinking comes amid escalating tensions in the ongoing US-Israeli conflict with Iran. According to Pentagon statements, one of the strategic objectives of the current military campaign is to significantly weaken Iran’s naval capabilities.
Search and rescue operations are still underway as Sri Lankan authorities and international agencies attempt to locate additional survivors or victims from the sunken warship.
