Iranian authorities have confiscated the American cargo of an oil tanker seized last year after US-led sanctions prevented the entry of medication into the Islamic republic, the judiciary said Wednesday.

The Marshall Islands-flagged Advantage Sweet was seized in April 2023 while sailing in the Gulf of Oman, a key route for the oil industry.

The vessel, chartered by Chevron Corp, had picked up oil from Kuwait and was bound for Texas before it was seized, an Advantage Tankers spokesperson said at the time.

The Iranian judiciary's Mizan Online website on Wednesday said a Tehran court "ordered the seizure of the American oil cargo on Advantage Sweet", with the cargo's value said to be worth more than $50 million.

It was not immediately clear when the court order was issued.

It said the oil seizure was in retaliation for "the sanctions of Western countries, especially the United States which led to the prevention of the sale of drugs needed for epidermolysis bullosa patients".

Iran has been under crippling US sanctions since Washington's 2018 withdrawal from a landmark nuclear deal.

In a 2021 report, United Nations experts cautioned that "over-compliance" with the sanctions had affected people suffering "from a severe and life threatening rare skin condition, epidermolysis bullosa, which causes extremely painful wounds".

The report came following the halt of shipments to Iran by a Swedish bandage company which reportedly offered the most effective treatment for the disease, according to the UN.

The Gulf of Oman has witnessed a series of hijackings and attacks over the years, often involving Iran.

In January, the US military said Iran was "holding five ships and over 90 crew members hostage from vessels seized nearly a year ago".