Farhan Al-Fartousi, from Iraq's General Company for Ports, told state television that one crew member had been killed and 38 rescued while the "search continues for the missing".

He did not specify the crew members' nationalities or provide details on who was behind the attack, which occurred roughly 50 kilometres (30 miles) from the coast.

However, India's embassy in Iraq said on Thursday an Indian national had died in the attack, with 15 other Indian crew members evacuated.

The Iraqi government's media cell told national news agency INA that "two tankers were subject to sabotage".

Iraq's oil ministry said on Thursday it had "deep concern" about incidents involving oil tankers in the Gulf.

"The safety of navigation in international maritime corridors and energy supply routes must remain free from regional conflicts," the ministry added.

The Strait of Hormuz, the waterway carrying a fifth of the world's oil, remains closed to almost all oil tankers, and Iran has vowed that not one litre of oil would be exported from the Gulf while its war with the United States and Israel continues.

US President Donald Trump said Wednesday that US forces have struck 28 Iranian mine-laying vessels more than a week into the Middle East war.

Iraqi state television channel Al-Ikhbariya broadcast images of a ship at sea with plumes of smoke rising from a huge fire.

An employee at Iraq's Basra oil terminal told AFP that it was unclear "whether it was a drone attack or explosive-laden boats".

The Iraqi State Organisation for Marketing of Oil (SOMO) confirmed in a statement that two oil tankers were attacked, without providing details on how.

Maltese-flagged oil tanker ZEFYROS was attacked as it was preparing to enter the port of Khor Al-Zoubair, where it would have taken on board an additional 30,000 tons of liquid naphtha -- primarily used in petrochemicals, SOMO said.

The second targeted vessel, SAFESEA VISHNU, was sailing under the Marshall Islands flag and was chartered by an Iraqi company, according to SOMO.

The incidents come just hours after the US embassy in Baghdad warned that Iran and Tehran-backed Iraqi armed groups might target US-owned oil facilities in Iraq.