Oil tankers stuck in the Persian Gulf for months began leaving on Thursday. They sailed through the Strait of Hormuz for the first time since the Iran war began.

Most ships followed Iran's approved route close to its coastline. Iran's Revolutionary Guard warned that any ship not following its route "will be dealt with accordingly." Ship traffic through the strait doubled in 24 hours.

That was the highest level since late February. The Liberian-flagged vessel Stoic Warrior was among the tankers that passed through.

But movement stayed cautious. At least three ships turned back on Thursday.

Traffic is still far below the pre-war level of over 100 daily crossings. Oil prices fell as investors expected global crude supplies to improve.

Brent crude dropped to $72.24 a barrel on Thursday. That is below the price before the Iran war started.

The war began on 28 February when the US and Israel launched missile attacks on Tehran. The traffic resumed after the US and Iran agreed to reopen the strait free of charge for 60 days.