The largest warship in the Iranian navy caught fire and later sank in the Gulf of Oman under unclear circumstances, semi-official news agencies reported.

The Fars and Tasnim news agencies said efforts failed to save the support warship Kharg, named after the island that serves as the main oil terminal for Iran.

The blaze began around 2.25am and firefighters tried to contain it, Fars said.

The vessel sank near the Iranian port of Jask, some 790 miles southeast of Tehran on the Gulf of Oman near the Strait of Hormuz, the narrow mouth of the Persian Gulf.

Photos circulated on Iranian social media of sailors wearing life jackets evacuating the vessel as a fire burned behind them.

State TV and semiofficial news agencies referred to the Kharg as a “training ship”.

Fars published video of thick, black smoke rising from the ship early Wednesday morning.

Satellite photos from Planet Labs Inc analysed by The Associated Press showed the Kharg off to the west of Jask on Tuesday.

Satellites from the US National Oceanic and Atmospheric Administration that track fires from space detected a blaze at the site of the Jask that started just before the time of the fire reported by Fars.

The Kharg serves as one of a few vessels in the Iranian navy capable of providing replenishment at sea for its other ships.

Iran Navy Fire
The Kharg was Iran’s largest warship (Asriran.com/AP)

It also can lift heavy cargo and serve as a launch point for helicopters.

The warship, built in Britain and launched in 1977, entered the Iranian navy in 1984 after lengthy negotiations that followed Iran’s 1979 Islamic Revolution.

Iran’s navy typically handles patrols in the Gulf of Oman and the wider seas, while the country’s paramilitary Revolutionary Guard operates in the shallower waters of the Strait of Hormuz and the Persian Gulf.

In recent months, however, the navy launched a slightly larger commercial tanker called the Makran it converted into serving a similar function as the Kharg.

Iranian officials offered no cause for the fire aboard the Kharg.

However, it comes after a series of mysterious explosions that began in 2019 targeting ships in the Gulf of Oman.

The US Navy later accused Iran of targeting the ships with limpet mines, timed explosives typically attached by divers to a vessel’s hull.

Iran denied targeting the vessels, though US Navy footage showed members of Iran’s Revolutionary Guard removing one unexploded limpet mine from a vessel.

The incidents came amid heightened tensions between the US and Iran after then-president Donald Trump unilaterally withdrew America from Tehran’s nuclear deal with world powers.

The sinking of the Kharg marks the latest naval disaster for Iran.

In 2020 during an Iranian military training exercise, a missile mistakenly struck a naval vessel near the port of Jask, killing 19 sailors and wounding 15.

Also in 2018, an Iranian navy destroyer sank in the Caspian Sea.