Four commodity vessels transited the Strait of Hormuz in the Persian Gulf on Thursday, down from six a day earlier and below the 10-day average of about 16, preliminary shipping data showed on Friday.
The figures could change as some ships typically switch off their transponders during the voyage to avoid the risk of detection in the conflict zone.
Of the four vessels, three were entering the strait heading into the gulf and one was exiting, the data from shiptracker Kpler showed at 02:00 GMT.
The vessels included two Panamax tankers, one supramax ship and one Kamsarmax vessel. The waterway carried a fifth of the world's oil and gas before the Iran conflict.
Three liquefied natural gas vessels also reappeared outside the Strait of Hormuz on Thursday, according to Kpler data.
Al Daayen and Al Samriya, both carrying cargoes loaded at Ras Laffan in Qatar, were last seen inside the strait on September 13 and 14, respectively. Al Samriya, controlled by QatarEnergy, and Al Daayen, owned and managed by Seapeak, are now both outside the strait.
The third vessel, Marigold LNG, which is operated by Kratos Gas Transport, is signalling for arrival at Dabhol, India after loading at Das Island in the United Arab Emirates.
In a report on Wednesday, Vortexa said the QatarEnergy-linked vessel Al Rayyan engaged in a so-called dark ship-to-ship (STS) cargo transfer with another Qatari carrier off the coast of Oman, meaning the vessels had their transponders switched off, without giving the timing of the transfer.
Kpler data showed Al Rayyan conducted an STS transfer with a ship called Al Mashabiyyah on September 13.
QatarEnergy, UAE-based Kratos Gas Transport, and Seapeak, an independent owner and operator of gas carriers, did not immediately respond to requests for comment.
In the Bab el-Mandeb Strait, 23 commodity vessels on Thursday transited the waterway, another maritime chokepoint on the southwest tip of Yemen and a vital trade route for oil between the Red Sea and the Gulf of Aden.
The data showed 13 vessels heading towards the Red Sea and 10 towards the Gulf of Aden. They included a Panamax and a Suezmax tanker, four supramax vessels and six Aframax tankers.
The number compares with an average of around 26 ships using the strait in the past 10 days.
The Iran-backed Houthis have seized Yemen's entire Red Sea coastline since last week, prompting the Saudi Arabian air force to conduct airstrikes.
The spread of the war to Yemen and Saudi Arabia has raised new concerns about oil supplies by jeopardising the Red Sea route for exports, the main alternative for gulf supplies while traffic through the Strait of Hormuz is constrained.
(Reporting by Emily Chow; Editing by Jacqueline Wong, Neil Fullick and Christian Schmollinger)