The US Treasury has revoked a general licence authorising the sale of Iranian oil after three tankers were struck in the Strait of Hormuz on July 6 and 7, according to a document released by the US. 

The move raises pressure on Tehran as it negotiates with Washington over reopening the waterway, testing a fragile ceasefire and pushing oil prices to two-week highs as attacks on shipping cast doubt on the durability of the accord.

A US official said the Office of Foreign Assets Control had rescinded the waiver to impose consequences on Iran because its actions in the strait were "wholly unacceptable," according to the newspaper.

"The MOU in effect with Iran is entirely performance-based. Iran will only reap benefits if they exhibit good behaviour," the official said, referring to the accord signed last month to extend the ceasefire for 60 days.

Brent crude settled 3% higher on July 7 at $74.16 a barrel and climbed as much as 6.1% in after-hours trading to a two-week high of $76.36.

UK Maritime Trade Operations said a tanker caught fire after being hit by an unknown projectile near the entrance to the strait, close to Oman, on the night of July 6, with two more tankers struck in a similar area the following day, one by a drone. One suffered structural damage.

Qatar's foreign ministry confirmed the first ship struck as the Al Rekayyat, a laden LNG tanker belonging to QatarEnergy.

Ministry spokesperson Majed al-Ansari described it as an unacceptable attack on the security of navigation and energy supplies and a grave violation of international law, holding Iran fully legally responsible.

One person said another of the ships hit was a Saudi crude tanker, though the situation was being investigated.