On Wednesday, March 4, 2026, Reuters reported that the Iranian light guided-missile frigate IRIS Dena (75), a Moudge-class vessel, sank in international waters about 40 km south of Galle, off Sri Lanka’s southern coast in the Indian Ocean. The Sri Lanka Navy rescued 32 of the 180 crew members; the rest are still missing and being searched for. The incident occurred at around 6:00 a.m. local time (12:30 GMT).
Photo: Fars News Agency
A spokesperson for the Sri Lankan Ministry of Defence told Reuters that the Sri Lanka Navy and Sri Lanka Air Force launched a rescue mission consisting of two vessels and a search-and-rescue aircraft after receiving an SOS signal from the Iranian ship. Foreign Minister Vijitha Herath did not provide further details but said Sri Lanka would take appropriate steps.
Local media reported that the crew had reported a malfunction off the coast near Galle in the south of the country, and that the injured were admitted to a hospital in Galle. Speculation has appeared in the public sphere (including from opposition voices in the Sri Lankan parliament) about an explosion or an attack – for example by a submarine – in connection with the ongoing war with Iran, but there is currently no evidence.
IRIS Dena (75) was the fourth Moudge-class ship to be built, out of five constructed and seven planned in total. The keel was laid in 2012, the hull was launched in 2015, and the ship entered service on June 13, 2021.
The Moudge class is 95 m long, 11.1 m wide, has a draft of 3.25 m, and a displacement of 1,500 tons. It is powered by two diesel engines rated at 10,000 hp (7,500 kW) each and four generators rated at 740 hp (550 kW) each, enabling a top speed of 30 knots. Its main armament consists of four Noor or Kader anti-ship missiles. Other weapons include a 76 mm Fajr-27 naval gun, a 40 mm Fath-40 anti-aircraft gun, two 20 mm Oerlikon naval guns, four Mehrab surface-to-air missiles (a copy of the SM-1 or a naval variant of Ra’ad), two triple 324 mm ASW torpedo launchers, and two 12.7 mm machine guns. In the future, ships of this class are expected to be armed with a naval variant of the Sayyad-2 surface-to-air missile.
On March 1, the sinking of the sister ship IRIS Jamaran (76) by U.S. forces was confirmed during the ongoing Operation Epic Fury (to date, the United States has confirmed the sinking of 17 Iranian surface and submarine vessels of various types, though not all have been named).
However, the service history of these ships had been ill-fated even earlier. IRIS Damavand (77) sank on January 28, 2019, after striking a concrete breakwater at the entrance to Bandar-e Anzali port on the Caspian Sea. Jamaran (76), in turn, accidentally hit the multipurpose support ship Konarak (1409) of the Hendijan class with a Noor anti-ship missile during exercises on May 10, 2020.
On December 5, 2021, the under-construction Shiraz (ex-Talaieh) slipped off its blocks and capsized in dry dock while water was being pumped in. During repairs, it was decided to rebuild it as a signals intelligence (SIGINT) vessel, and it entered service on January 15, 2025 as Zagros (313).
Meanwhile, on July 7, 2024, during overhaul work in Bandar Abbas, an accident occurred in which Sahand (74) rolled onto its port side after an explosion on board. The vessel was raised and a decision was made to repair it; it returned to service on November 29, 2025.
UPDATE
According to new information from Reuters, citing sources in the Sri Lanka Navy and the Sri Lankan Ministry of Defence, the Iranian frigate was sunk by an unidentified submarine. The latest tally is 78 injured and 101 missing.
“At this point, we know that 79 people have been rescued and taken to hospital, and one of them was seriously injured. Another 101 are believed to be missing, and the ship sank,” said a Sri Lanka Navy source who declined to be named because he was not authorized to speak to the media. One of the crew members taken to hospital died.
UPDATE 2
U.S. Secretary of Defense Pete Hegseth said at a press conference that the Iranian ship had been torpedoed by the U.S. Navy (US Navy).
“An Iranian warship that thought it was safe in international waters… Instead, it was sunk by a torpedo – the first ship sunk by a submarine since World War II,” Hegseth said.
LIVE: @SecWar and Chairman of the Joint Chiefs of Staff, Air Force Gen. Dan Caine, hold a press briefing at the Pentagon. https://t.co/0NijeaLSOO
— Department of War 🇺🇸 (@DeptofWar) March 4, 2026
UPDATE 3
Another Iranian warship has been attacked by U.S. forces: the guided-missile corvette IRIS Shahid Sayyad Shirazi, a Shahid Soleimani-class vessel belonging to the Islamic Revolutionary Guard Corps Navy (IRGCN) (Sepāh-e Pāsdārān-e Enqelâb-e Eslâmī), was hit in the Strait of Hormuz, near the port of Bandar Abbas. This means the United States has now sunk 19 Iranian surface and submarine vessels of various types.
The IRIS Shahid Sayyad Shirazi, a Soleimani-class corvette serving with Iran’s Islamic Revolutionary Guard Corps Navy (IRGCN), has been targeted by U.S. strikes in the Strait of Hormuz, off the coast of Bandar Abbas, Hormozgan Province. pic.twitter.com/MNBtPQXsc0
— OSINTdefender (@sentdefender) March 4, 2026
UPDATE 4
The U.S. Department of Defense released video footage from the optoelectronic periscope of a U.S. nuclear-powered submarine that sank the frigate IRIS Dena (75). According to the Chairman of the Joint Chiefs of Staff, Gen. Dan Caine, a single 533 mm heavy torpedo – the Lockheed Martin Mk 48 Mod 7 CBASS (Common Broadband Advanced Sonar System) – was used.
https://t.co/PiqQpVIrMu pic.twitter.com/Wc1e0B0um7
— Department of War 🇺🇸 (@DeptofWar) March 4, 2026
UPDATE 5
According to CENTCOM, the number of sunk Iranian vessels has exceeded 20.
U.S. forces have struck or sunk to the bottom of the ocean more than 20 ships from the Iranian regime. Last night, CENTCOM added a Soleimani-class warship to the list. pic.twitter.com/KgW8cS726P
— U.S. Central Command (@CENTCOM) March 4, 2026