The United States Navy conducted a submarine attack that resulted in the sinking of the Iranian frigate IRIS Dena in the Indian Ocean, approximately 200 nautical miles east of Sri Lanka. Multiple independent sources, including Reuters, Naval News, and Fox LA, confirm the engagement, which occurred as the vessel was returning from a naval exhibition hosted by India in Visakhapatnam. The attack was carried out by a US submarine, which launched a torpedo that struck the IRIS Dena, leading to its rapid sinking. Footage released by defense media outlets shows the moment of the torpedo launch and impact, corroborating the sequence of events.

Casualty figures are consistent across reporting, with at least 83 Iranian sailors confirmed dead, according to the Maritime Executive and Reuters. The Indian Navy responded to a distress call from the IRIS Dena shortly after the attack, though no rescue operations were reported as successful. A second Iranian naval vessel altered course and entered Sri Lankan waters, docking in Trincomalee. Sri Lankan authorities evacuated the crew, citing safety concerns and regional instability. The move underscores growing apprehension among Indian Ocean littoral states about the spillover of broader geopolitical conflicts into regional waters.