Iran's biggest navy warship sank on Wednesday (June 2).
The country's highest-tonnage navy vessel, known as the Kharg, caught fire in the Gulf of Oman near the port of Jask, where it was on a training mission.
All of its crew members disembarked safely, following rescue operations that went on for hours.
But efforts to save the ship itself were unsuccessful and it sank, according to Fars news agency.
No further explanation has been given for the latest incident in the region of sensitive waterways.
Though there have been accusations of attacks on ships owned by arch-enemies Iran and Israel there in the past.
Iran has refused to recognize Israel since the Islamic Revolution in 1979 that toppled the U.S.-backed Shah.
And Israel sees Iran's nuclear program as a threat to its existence.
Both parties have claimed they were targeted by the other in the last few months.