WASHINGTON - US Defense Secretary Pete Hegseth said Wednesday that a US submarine sank an Iranian warship in international waters.

"An American submarine sunk an Iranian warship that thought it was safe in international waters," Hegseth said at the Pentagon briefing on Wednesday. "Instead, it was sunk by a torpedo."

He further said it was the first sinking of an enemy vessel by a torpedo since World War II.

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At least 80 people on board the Iranian frigate IRIS Dena were killed after the vessel was attacked and sunk by the US submarine in the Indian Ocean off the southern coast of Sri Lanka, Sri Lanka's Deputy Minister of Foreign Affairs Arun Hemachandra said Wednesday.

The Iranian warship had taken part in a naval exercise held in the Bay of Bengal from Feb 18 to 25, according to the drill's website.

The US Central Command (CENTCOM) said Wednesday that US forces have struck or sunk more than 20 Iranian vessels since the United States and Israel began a military operation against Iran on Saturday morning.

"Last night, CENTCOM added a Soleimani-class warship to the list," the command said on X.