Various industry sources and news agency reports say that Iran's oil exports in May have mostly stopped, with a maximum of 400 barrels per day (bpd) being shipped to unknown Asian destinations.

Reuters news agency says Iranian crude exports have fallen sharply in May to around 400,000 (bpd), according to tanker data and two industry sources.

Bloomberg says no tanker departures from Iran's export terminals have been observed.

The United States imposed sanctions on Iran's oil exports in November but was allowing limited purchases by several countries until May, when it ended the reprieve.

The U.S. administration has vowed to cut Iran's oil exports down to zero and all indications are that it is practically working.

Even if Iran sold 400,000 bpd, that is only a fraction of what it exported one year ago, which would put a huge dent into the country's budget. More than 40 percent of known government expenditures are financed by oil sales.

Iran was selling more than two million bpd before the U.S. pulled out of the nuclear agreement and began imposing sanctions.

Iran has nonetheless sent abroad about 400,000 bpd so far this month, according to data from Refinitiv Eikon and two industry sources who also track the flows, less than half April's rate. The bulk of the crude is heading to Asia.

It is also more likely that the oil is not being unloaded anywhere but being stored either on tankers or at some storage facility. China is currently storing 20 million barrels.