Visible crude loadings from the Red Sea port of Yanbu fell by at least 30 per cent last week after Yemen's Houthis declared a blockade on Saudi Arabia, Kpler and AXSMarine data showed, though Vortexa estimated that exports remained broadly stable, citing a rise in so-called dark tanker loadings.
Yanbu, Saudi Arabia's main Red Sea oil export hub, is a key outlet for crude shipped westward to Europe and North America via the SUMED pipeline and Red Sea routes, avoiding the Strait of Hormuz.
The focus on Yanbu has intensified as the Red Sea has emerged as a new front in the regional conflict that began with the US-Israeli attacks on Iran on February 28.
Data from Kpler, Signal Ocean and AXSMarine shows average exports of crude and condensate fell to between 2.4 million and three million barrels per day in the week commencing July 20. Exports in the previous week had averaged 4.23 million bpd, according to Kpler.
Loading voyages fell to 16 last week from 35 in the previous week, AXSMarine said, while noting that its analysis is based on AIS data and may not capture all loadings by vessels operating with their transponders switched off, known as going dark.
Saudi state oil company Aramco did not respond immediately to a request for comment.
Data from Vortexa showed loadings at 3.8 million bpd last week, broadly stable from the previous week. The company said the use of dark loads had increased, with four VLCCs, one Suezmax and one Aframax loading with AIS transponders switched off, accounting for about a third of volumes lifted during the week.
Broker Clarksons expects Yanbu exports to remain steady at about four million bpd in the first three weeks of July.
(Reporting by Ahmad Ghaddar and Jonathan Saul Editing by Alex Lawler and David Goodman)