US Secretary of Defense Pete Hegseth has said an American submarine sank an Iranian warship in the Indian Ocean.

It came after a Sri Lankan defence official told BBC Sinhala around 140 people were feared missing after the Iris Dena sent out a distress call early on Wednesday morning.

The island nation’s navy confirmed it had rescued 32 people from the ship, which sunk in waters about 40km (25 miles) south of its coast.

Search and rescue operations are ongoing. The survivors were “seriously injured” and taken to hospital in the southern port of Galle, foreign affairs minister Vijitha Herath said.

Hegseth told a news conference that a US submarine had sunk an Iranian warship “that thought it was safe in international waters”.

“Instead it was sunk by a torpedo. Quiet death.”

Earlier, Sri Lankan navy spokesman Budhika Sampath had rejected reports that the Iris Dena had been attacked by a submarine.

He told BBC Sinhala that 180 people were believed to have been on board, according to the ship’s documentation.

He added that at the time of launching the rescue operations they did not see the vessel – nor any other ships in the region – but saw oil patches on the water and floating life rafts.

Though the ship’s location “was beyond our waters,” Sampath said, “it was within our search and rescue region. So we were obliged to respond as per international obligations”.

First launched in 2015, the Iris Dena is a destroyer attached to Iran’s Southern Fleet.

It had recently participated in International Fleet Review 2026, a military exercise hosted by India. (BBC)