Rescue operations intensify off Sri Lanka’s southern coast as Washington confirms strike on IRIS Dena amid escalating U.S.–Iran tensions.

More than 140 sailors are feared missing after a United States submarine struck and sank an Iranian naval warship in the Indian Ocean, in what is being described as one of the most significant naval escalations between Washington and Tehran in recent years.

The vessel, identified as the Iranian Navy frigate IRIS Dena, reportedly went down after being hit by torpedoes launched from a U.S. submarine in international waters near Sri Lanka’s southern coastline. The incident triggered an immediate multinational search and rescue operation.

U.S. Defense Secretary Pete Hegseth confirmed that an American submarine carried out the strike, characterising the operation as a major military action amid rising hostilities between the two countries.

Sri Lankan authorities said approximately 180 personnel were believed to be on board at the time of the attack. At least 30 survivors have been rescued and transported to medical facilities in the southern city of Galle. However, more than 100 crew members — possibly as many as 140 — remain unaccounted for as search efforts continue.

Initial reports indicate that the IRIS Dena issued a distress signal shortly before it sank. Sri Lanka’s navy and air force responded swiftly after detecting an oil slick and floating debris at the site. By the time rescue teams arrived, the warship had reportedly disappeared beneath the surface.

While U.S. officials have acknowledged responsibility, some regional authorities initially described the sinking as a suspected submarine strike pending further investigation. The incident has heightened global concern over the risk of a broader conflict spilling into critical maritime routes in the Indian Ocean.

Commissioned in 2021, the IRIS Dena was one of Iran’s domestically built frigates and had recently participated in multinational naval engagements prior to the incident.

Rescue operations remain ongoing as authorities work to account for the missing sailors and determine the full circumstances surrounding the strike.