‘Execution at sea’: Was IRIS Dena, Iranian frigate sunk by US in the Indian Ocean, unarmed?

The sinking of the Iranian frigate IRIS Dena by a US submarine in international waters near Sri Lanka has raised questions over the circumstances of the attack, with Iran and strategic affairs experts suggesting that the warship may have been operating in a non-combat configuration and was “unarmed”.

The frigate was returning from India after participating in MILAN-2026, a multilateral naval exercise hosted by New Delhi in Visakhapatnam, before it was torpedoed by a US submarine, killing at least 87 sailors.

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Commenting on the incident, Strategic affairs expert Dr. Brahma Chellaney raised questions about the nature of the strike, arguing that if the ship was lightly armed or unarmed, and “the strike looks less like combat than a premeditated execution.”

“A Moudge-class frigate such as the IRIS Dena, even if fully armed, would be no match for a U.S. nuclear-powered attack submarine operating in India’s maritime backyard. But the circumstances matter. If the Dena carried little or no munitions — as the ‘peace protocol’ of India’s MILAN-2026 exercise requires — the strike looks less like combat than a premeditated execution,” Chellaney said.

He also raised a “nagging question” about whether India shared intelligence about IRIS Dena with the US under military pacts COMCASA and LEMOA, which may have played a role in locating the Iranian vessel.

“The Nagging Question: Did Shared Intelligence Sink the Iranian Frigate? Under the military pacts COMCASA and LEMOA, India and the U.S. share sensitive maritime data. If a U.S. attack submarine used shared data to locate and sink an Iranian frigate that had just departed an Indian port after participating in a multilateral naval exercise, it would represent a foundational breach of the defense partnership,” he said.

During the harbour phase of the MILAN exercise in Visakhapatnam, participating ships are required to remain in a “safe configuration”, which includes public tours, diplomatic engagements, and fleet reviews under strict safety protocols.

“If the Dena left the exercise area in such a restricted configuration, the imbalance between target and attacker becomes stark: a lightly armed — or possibly unarmed — guest ship departing a cooperative exercise, tracked and destroyed by the world’s most sophisticated undersea warfare platform,” Chellaney said.

The Nagging Question: Did Shared Intelligence Sink the Iranian Frigate? Under the military pacts COMCASA and LEMOA, India and the U.S. share sensitive maritime data. If a U.S. attack submarine used shared data to locate and sink an Iranian frigate that had just departed an Indian…

— Dr. Brahma Chellaney (@Chellaney) March 5, 2026

Iran claims ship was unarmed

Iran’s Ambassador to India Dr Mohammad Fathali, also condemned the attack, claiming the vessel was unarmed when it was torpedoed by the US submarine.

“We will respond to this assassination very strongly. This ship was unarmed and in a regular maneuver at sea. I think that the United States and the Zionist regime want to disturb and destroy all the international law and international norms,” Fathali said.

Opposition questions India’s silence

The Opposition Congress has also reacted to the incident, with its leader, Sachin Pilot, saying India should stick to its neutral and sensible position in global conflicts. “I hope there is an end soon, the loss of lives and properties will stop… India has always been neutral. India’s position has been like a sane, sensible, mature nation; we should stick to that,” Pilot said.

The Congress leader also questioned the government’s silence, asserting that the sinking of the Iranian vessel occurred in waters close to India’s area of influence.

“As far as action by America is concerned, they attacked suo motu… if there is one-sided activity in our area of influence, then somewhere, India’s territorial integrity, neutral stand that is there, if we don’t speak up, our silence is wrong,” he said.

‘Iranian vessel was struck far from India’s jurisdiction’

However, some in the country believe India bore no responsibility for the incident as the ship had already sailed 250 nautical miles away from India’s coastline. Suresh Nakhua, who describes himself as a BJP supporter, said the frigate was struck far from India’s jurisdiction.

“The strike on IRIS Dena occurred around 250 nautical miles from India’s coastline, in international waters and beyond India’s maritime jurisdiction. While India shares close maritime proximity with several countries across the Indian Ocean, geographical vicinity does not translate into responsibility for every incident in the region,” he added.