Escalating hostilities between Washington and Tehran expanded into the Indian Ocean after a United States submarine torpedoed the Iranian Navy frigate IRIS Dena off the southern coast of Sri Lanka, killing dozens of sailors and raising complex diplomatic questions for South Asia. The attack occurred as a broader military confrontation intensified following Israeli and American air strikes across Iran on February 28. The frigate was struck on March 4 in waters roughly 40 nautical miles from the Sri Lankan port of Galle while returning to Iran after participating in multinational naval events hosted by the Indian Navy. Officials confirmed that a US submarine fired a Mark 48 torpedo that hit the vessel, causing catastrophic damage and sending the ship to the seabed within minutes. Sri Lankan rescue teams recovered 87 bodies and pulled 32 survivors from the water while searching for additional crew members reported missing.
The sinking marked a rare use of submarine-launched torpedoes against a surface warship by the United States. Military analysts described the strike as the first confirmed instance of a US submarine destroying an enemy vessel in combat since the Second World War, underscoring how rapidly the confrontation with Iran has widened beyond the Gulf region.
Crew aboard the frigate had taken part in large international naval gatherings organised along the eastern seaboard earlier in February, including the International Fleet Review and the multinational MILAN exercise. These events drew warships from dozens of countries and were intended to showcase maritime cooperation and confidence-building among regional navies.
Diplomatic attention has also focused on New Delhi’s interactions with the Iranian vessels before the attack. According to officials familiar with the naval movements, authorities had permitted Iranian ships to seek safe harbour in local ports amid rising tensions in West Asia. One such vessel, IRIS Lavan, docked at the naval facility in Kochi with more than 180 crew members around the time the strike occurred, reflecting a humanitarian decision aimed at avoiding potential escalation at sea.
Officials in New Delhi have emphasised that the docking permissions were granted under established maritime protocols allowing visiting warships access to ports during exercises and emergencies. Naval authorities also responded to distress signals from the stricken frigate and coordinated with Sri Lankan counterparts in rescue efforts once the explosion was reported in the early hours of March 4.
Iran condemned the torpedo attack as an act of aggression, noting that the frigate had been operating in international waters after participating in a cooperative naval gathering. Iranian officials warned that Washington would face consequences, framing the incident as evidence that the widening conflict now threatens maritime routes far from the Middle East.
American officials defended the strike, describing the vessel as a legitimate military target amid ongoing hostilities between the United States, Israel and Iran. Defence authorities portrayed the operation as a demonstration of naval reach, highlighting the strategic role of submarines in modern warfare.
The attack unfolded against the backdrop of a rapidly escalating confrontation triggered by Israeli and US air strikes across Iran at the end of February. Those operations targeted military infrastructure and senior commanders, prompting retaliatory missile and drone attacks by Tehran against American interests and maritime traffic across the wider region.
Regional governments were drawn into the aftermath of the sinking as rescue and humanitarian responses unfolded. Sri Lanka dispatched naval and air units to the scene after receiving a distress call from the damaged frigate, recovering bodies and transporting survivors to medical facilities in the southern port city of Galle. Local authorities faced logistical challenges as morgues and hospitals processed casualties from the incident.
Another Iranian vessel, IRIS Bushehr, later sought assistance from Sri Lanka after mechanical difficulties during the same deployment. Authorities permitted the ship to dock at Trincomalee while its crew was temporarily accommodated at naval facilities, a move framed as a humanitarian measure by Colombo while emphasising neutrality in the unfolding conflict.
Strategic analysts say the destruction of the frigate illustrates how naval confrontation is spreading beyond traditional flashpoints. The Indian Ocean, a critical corridor linking the Middle East with East Asia, has long been considered a zone of strategic competition among major powers. The attack on the Iranian vessel near Sri Lanka placed the conflict on the doorstep of one of the world’s busiest maritime trade routes.