Top buyers China, India, Japan and South Korea imported a total 1.62 million barrels per day (bpd) of crude from Iran in April, up 3.2pc from the previous month to the highest since July, the data showed.

China's imports in April nearly touched 800,000 bpd, a level not seen since 2014 when global powers and Iran were working on an agreement to curb Tehran's nuclear programme.

South Korea became the second-largest importer of Iranian oil in April after India scaled back, with Korea's imports at about 416,000 bpd, the highest for the country since 2017.

The world's fifth-largest crude oil importer had been heavily reliant on Iranian condensate, an ultra light oil used for petrochemical production.

Still, the four countries' imports are down 24pc in the first four months this year, compared with the same period a year ago because of the sanctions, the data showed.

Last November, the United States allowed Iran's eight largest buyers to continue importing oil from Tehran for 180 days, but Washington announced in April that it will not extend the waivers.

US Special Representative for Iran, Brian Hook, reiterated on Thursday that the United States will sanction any country which buys oil from Iran after the expiration of waivers on May 2.

Japan and South Korea have stopped importing Iranian oil in May.

China is expected to receive close to 11 million barrels of Iranian oil this month, while 4 million barrels have been discharged in India in May, according to data on Refinitiv Eikon.