Iran on Friday announced the reopening of the strait, which it has effectively blocked during the Middle East war, before closing it again a few hours later on Saturday, citing the continued US blockade on Iranian ports.

After a peak in crossings by 26 raw materials carriers on April 18, the number of transits has dropped to its lowest level since the war began, according to maritime data from Kpler.

From April 19 to 22, only 18 vessels passed through the strait, an average of 4.5 per day. By comparison, between March 1 and April 17, around nine ships -- double that figure -- crossed daily.

About 120 daily transits are recorded during peacetime, according to maritime information site Lloyd's List.

Traffic is therefore currently down by more than 96 percent from normal levels.

- Ship attacks -

At the same time, the number of incidents reported by vessels in the area has increased.

Seven attacks or incidents have been recorded by the security agency United Kingdom Maritime Trade Operations (UKMTO) and/or intelligence firm Vanguard Tech since Saturday.

Five of those have been confirmed by the International Maritime Organization (IMO).

No incidents had been reported before those attacks since April 7.

Since the start of the war, 38 incidents have been recorded by UKMTO, Vanguard and/or the IMO.

The two most recent incidents confirmed by the IMO occurred on Wednesday and involved the Epaminondas, flying the Liberian flag, and the Euphoria, flying the Panamanian flag.

Iran's Revolutionary Guards said they had intercepted the Epaminondas.

Tehran demands that vessels obtain authorisation to enter or leave the Gulf via the Strait of Hormuz.

The route in peacetime sees the passage of around a fifth of global oil and gas exports, as well as other key commodities.

It has been largely blocked since the war started with US and Israeli strikes against Iran on February 28.