"Reported attacks on Japan-related tankers occurred while PM @AbeShinzo was meeting with Ayatollah @khamenei_ir for extensive and friendly talks. Suspicious doesn't begin to describe what likely transpired this morning," Mohammad Javad Zarif tweeted.

Japanese Prime Minister Shinzo Abe met Iran's supreme leader Ayatollah Ali Khamenei on Thursday morning, seeking to ease soaring tensions between Tehran and Washington.

Foreign ministry spokesman Abbas Mousavi too expressed "concern" over the coincidence of the reported tanker attacks with Abe's visit, saying it was "against regional and trans-regional efforts... towards reducing tensions."

"Iran supports cooperation and talks in the region," he added.

One of the two tankers -- Kokuka Courageous -- belongs to the Japanese company Kokuka Sangyo Ltd, the head of the company told reporters.

The ship's owners confirmed their tanker had been attacked and that all of its 21 crew members had been rescued.

Iran's navy rescued 44 sailors in all from the Kokuka Courageous and the Norwegian-owned Front Altair after fires broke out on both vessels.

The crews were brought to Bandar-e Jask port in the southern province of Hormozgan.

"The fire has been extinguished" aboard the Kokuka Courageous, head of Hormozgan ports and maritime organisation Allahmorad Afifipour said in an interview aired on state television.

"We are still assessing whether the crew can be transferred back to their ship," he added.

Fire was still burning on the Front Altair, according to the official, and Iranian assistance was continuing.

According to Iranian state media, the Front Altair was carrying ethanol from Qatar to Taiwan, while the Kokuka Courageous was carrying methanol from Saudi Arabia to Singapore.