Attacks on commercial vessels in the Gulf have climbed to unprecedented levels since the war began, with 24 ships targeted in the first two weeks of October, according to figures published by the Financial Times. That is roughly double the 13 vessels hit during the opening fortnight of the conflict.

The UK Maritime Trade Operations agency said on Saturday that two oil tankers had come under attack off the Saudi coast on Friday evening. The first was struck by an unidentified projectile 68 nautical miles northeast of Jubail, forcing the evacuation of its crew, none of whom were hurt. The master of a second tanker reported that his ship had been hit by a rocket-propelled grenade fired from a small boat 78 nautical miles from Jubail, damaging its stern. The agency said that crew had been located and were safe.

Maritime security firm Vanguard identified one of the vessels as the Marshall Islands-flagged tanker ST 3, saying its crew had been transferred to a nearby UAE-flagged container ship.

Iran's Revolutionary Guard navy said a tanker carrying more than two million barrels of crude caught fire after striking a sea mine while transiting the Strait of Hormuz on a route Tehran does not permit. US Central Command rejected that account, saying the shipping lanes used were free of mines and that the damage was caused by Iranian projectiles or drones.

The disruption is choking supply. Data from Kpler show oil exports fell from an average of 15.5 million barrels a day in September to 2.9 million on October 11. Brent crude closed Friday near $110 a barrel, its highest level since May.

The strait has been at the centre of the US-Iran confrontation since the war began on February 28.