An oil tanker damaged in a suspected attack in the Gulf of Oman sunk on Thursday afternoon, Iranian news agency IRNA reported.
Earlier reports had said the tanker, named the Front Altair, was carrying 75,000 tons of naphtha, a flammable liquid hydrocarbon.
Meanwhile, a Frontline company spokesman denied the Iranian reports, saying the Front Altair was still afloat.
"There are pictures from a salvage vessel that is circling the ship, and the vessel hasn't sunk," said company spokesman Pat Adamson, citing the most recent information received from the ship's technical management.
Iranian search and rescue teams reportedly picked up 44 sailors from the Front Altair and another damaged tanker, the Islamic Republic News Agency reported, citing an unnamed informed source.
The sailors were taken to the Iranian port of Jask, IRNA reported.
Twenty-three crew on the Front Altair, a Marshall Islands-flagged tanker heading from Qatar to Taiwan, abandoned ship when a fire broke out approximately 25 miles from Jask.
The second tanker was a Panama-flagged ship, named Kokuka Courageous, heading from a port in Saudi Arabia toward Singapore when a fire broke out approximately 28 miles from Jask.
Twenty-one crewmen abandoned that ship and were picked up by Iranian search and rescue teams, IRNA reported.
Oil prices jumped as much as 4% on Thursday after the suspected attack.
Iranian Foreign Minister Mohammad Javad Zarif called the suspected attacks "suspicious" and called for regional dialogue to avoid tensions.
Zarif tweeted that "reported attacks on Japan-related" oil tankers in the Gulf of Oman had taken place while Japanese Prime Minister Shinzo Abe was meeting Iran's Supreme Leader Ayatollah Khamenei "for extensive and friendly talks".
"Suspicious doesn't begin to describe what likely transpired this morning," he tweeted. "Iran's proposed Regional Dialogue Forum is imperative."
The US Navy's 5th Fleet said earlier that it was assisting the Front Altair and Kokuka Courageous, as they were under apparent attack in the Gulf, which connects the Arabian Sea with the Strait of Hormuz, a major strategic waterway through which a fifth of global oil consumption passes from Middle East producers.
The United Kingdom Maritime Trade Operations, part of the Royal Navy, said it was aware of an incident in the Gulf of Oman.
"The UK and its partners are currently investigating," the group said without elaborating.
One shipping broker said there had been an explosion "suspected from an outside attack" that may have involved a magnetic mine on the Kokuka.
Another source said the Front Altair reported a fire caused by a "surface attack" and that the crew had been picked up by nearby vessel Hyundai Dubai.
There was no immediate confirmation of the incident from authorities in Oman or the United Arab Emirates, in whose territorial waters four tankers were hit last month.
The UAE had said that the May 12 attacks on four vessels off the coast of Fujairah, a main bunkering hub, were likely caused by limpet mines and bore the hallmarks of an operation, most likely by a state actor.
Saudi Arabia's envoy to the United Nations blamed Iran. Tehran has denied any involvement.
