Ships were largely avoiding the Strait of Hormuz on Monday after an escalation at the weekend in which Iran fired what appeared to be warning shots at vessels and the US military seized an Iranian cargo ship.
Just one ship exited the Persian Gulf through the strait while two entered in the space of 12 hours, ship-tracking data showed on Monday, a fraction of what is usually about 130 vessels per day.
The oil products tanker Nero, which is under British sanctions for Russia-related activities, was sailing through the strait, satellite analysis from SynMax and tracking data from the Kpler platform showed.
Two other ships - the chemical tanker Starway and Axon I, a liquefied petroleum gas tanker under US sanctions for past trading with Iran- were sailing into the gulf.
More than a dozen tankers passed through the strait after Iran briefly declared it open on Friday. But a ceasefire between the United States and Iran appeared in jeopardy on Monday as Iran vowed to retaliate for the US seizure of its vessel and refused to join new peace talks.
Oil charterers had been preparing tankers to leave the gulf after the announcement on Friday.
That announcement triggered a sharp fall in oil prices and war risk insurance rates started to fall.
Those rates have since risen again, to levels around three per cent of the value of the ship from two per cent, shipping and insurance sources said.
"Recent weeks have brought several false starts and, although some form of resolution is likely at some point, the timing of any durable breakthrough remains highly uncertain," ship broker Clarksons said in a note on Monday.
Iran fired shots at ships in the strait on Saturday, including a container ship belonging to CMA CGM, the French firm confirmed, describing them as "warning shots" and adding that the crew were safe.
With a view to cooling soaring oil prices, the Trump administration on Friday renewed a waiver on sanctions on Russian oil at sea, allowing buying to resume for about a month.
Oil prices were up about five per cent on Monday on fears that the ceasefire between the United States and Iran could collapse and as traffic through the strait remained largely halted.
Brent crude futures were up 3.8 per cent to $94.75 a barrel by 13:25 GMT and US West Texas Intermediate was up 4.0 per cent at $87.82 by 13:29 GMT.
Two days earlier, Treasury Secretary Scott Bessent had said Washington would not be renewing the waiver. A similar one-month sanctions waiver allowing Iran to export crude oil and products lapsed on Sunday.
India, which has been a top buyer of Russian crude while others have demurred since Moscow’s invasion of Ukraine in 2022, named three more Russian insurers that it will allow to offer marine cover to shippers.
The now 11 Russian companies it recognises are not part of the International Group of PI Clubs, which provides liability cover for personal injury or environmental clean-up claims for the majority of the world's tankers.
(Reporting by Jonathan Saul in London, Nerijus Adomaitis in Oslo, Gus Trompiz in Paris, Nidhi Verma in New Delhi, Ismail Shakil in Ottawa, Timothy Gardner and Jasper Ward in Washington, Gleb Bryanski in Moscow; writing by Jason Neely, editing by Kevin Liffey)
