U.S. Submarine Sinks Iranian Frigate IRIS Dena off Sri Lanka

Iranian Navy frigate IRIS Dena was sunk by a torpedo fired from a United States Navy submarine in the Indian Ocean off the southern coast of Sri Lanka, marking a rare instance of submarine warfare in modern naval conflict. The attack occurred in international waters roughly 19 nautical miles from Galle, while the vessel was returning to Iran after participating in MILAN 2026, an international naval exercise hosted by India in the Bay of Bengal. According to statements from the U.S. Department of Defense, the submarine fired a Mark 48 torpedo, striking the Moudge-class frigate and causing it to sink within minutes. U.S. Defense Secretary Pete Hegseth confirmed the action during a Pentagon briefing, describing the strike as a torpedo engagement against an Iranian warship operating in the region. Reports indicate that around 180 personnel were on board at the time of the attack. The Sri Lanka Navy and Sri Lanka Air Force launched a search and rescue operation after receiving a distress call from the vessel at 05:08 Sri Lanka Standard Time. Naval ships, aircraft, and medical teams were deployed from the southern port area. By the end of the operation, 87 bodies had been recovered, while 32 sailors were rescued alive and transported to Karapitiya Teaching Hospital in Galle for treatment of injuries and exhaustion. Approximately 60 crew members remained missing after the sinking. The IRIS Dena was one of Iran’s modern Moudge-class guided-missile frigates, commissioned in the early 2020s as part of Iran’s naval modernization program. The attack took place during an expanding military confrontation involving the United States, Israel, and Iran, known as Operation Epic Fury, which began on 28/02/2026 with strikes on Iranian military infrastructure. By early March, U.S. officials stated that multiple Iranian naval vessels had been destroyed in the campaign across the Persian Gulf and surrounding waters. Following the sinking, Sri Lankan authorities continued maritime patrols and coordinated with regional partners, including India, to search for survivors. The incident also prompted diplomatic responses, with Iran condemning the attack and requesting assistance for repatriation of recovered bodies. The event extended the geographic scope of the conflict from the Middle East into the Indian Ocean region near Sri Lanka.