Ships transiting the Strait of Hormuz face a "heightened and increasingly unpredictable kinetic threat" given the recent sharp increase in traffic, Marisks, a shipping intelligence service, said on Saturday.
The seven-day moving average for crude exports from the region was 18.3 million barrels per day on September 30, provisional data from Kpler showed, with volumes topping pre-war levels on 14 days in September.
That included Gulf oil sent Hormuz, via the Red Sea, and from terminals and ship-to-ship transfers in the Gulf of Oman.
Shipments had earlier matched or exceeded pre-war levels on a handful of days in June and July, Kpler data showed, after Washington and Tehran reached a memorandum of understanding that has since lapsed.
Crude exports from the region averaged about 18 million bpdin the 12 months before the start of the US-Israeli war with Iran, according to Kpler.
The recent export surge has been driven by Saudi Arabia loading from both the Red Sea and the Gulf, three weeks after a September 10 attack on its East-West pipeline, Kpler said.
It has required more supertankers to shuttle crude through Hormuz, trade sources and analysts have said, adding that ship-to-ship transfers in the Gulf of Oman have reached their limits.
Iraq's state-owned Oil Tanker Company and some refiners have chartered tankers to load Basrah crude inside the strait after Baghdad secured Iranian permissionin August for Iraqi oil tankers to pass through Hormuz.
Shipping data provider Vortexa also said Gulf flows have recovered. It said that the 14-day moving average for Middle East crude and condensate exports hit 18.6 million bpd, exceeding the 10-year seasonal average and returning to pre-conflict levels.
"Most of this month-over-month increase seen in September comes from Saudi Arabia, which is ramping up exports to regain market share from other Middle Eastern countries," senior market analyst Xavier Tang said.
"This increase in Middle East supplies will also help alleviate tightness in the oil market, especially for Asian refiners," he said.
Liquefied natural gas cargoes exiting the Strait of Hormuz also rose in September to their highest since February.
However, attacks on tankers continued, with at least seven incidents reported in the past week, Marisks said, noting the very large crude carrier (VLCC) Kazimah III was struck on October 1 by an unknown projectile while in the strait, causing a fire onboard. Its owner, Kuwait Oil Tanker Company, did not respond to a request for comment.
The United Kingdom Maritime Trade Operations agency has reported at least one attack a day in the Strait of Hormuz or the Gulf of Aden since October 2.
Marisks said "the recent pattern of incidents may not necessarily represent deliberate targeting of individually selected merchant vessels.
"Instead, available information indicates the possibility that Iranian forces are launching missiles into a predetermined engagement area or 'kill box', with weapons potentially acquiring and locking onto available radar signatures within that area."
Before the Iran war started on February 28, the strait typically handled about 125 large commercial vessels per day, including tankers, gas carriers, bulkers and container vessels, accounting for some 20 per cent of global crude and LNG supply.
