The attacks renewed concerns about the recovery of global oil supplies and shipping, and highlighted the fragility of an interim truce while the US and Iran hammer out a lasting agreement.
Oil prices eased on Friday but remained on track for weekly gains of 4-5 per cent after the flare-up.
The International Energy Agency said global oil supply rose by 4.1 million barrels per day in June as shipping through the strait resumed but remained 9.4 million bpd below pre-war levels.
It warned of tight diesel and petrol supplies, and said refineries were slower to react to the reopening of the strait than crude prices.
Only 22 ships passed through the strait on Thursday.
On Wednesday, the number of transits stood at 30, according to a report from data and analytics company Kpler.
A week ago on Thursday - before the latest outbreak of fighting - 48 vessels passed through the strait, Kpler said.
Data provider Windward also noted in an analysis published on Thursday that shipping traffic out of the Gulf had "effectively stopped".
The Strait of Hormuz handled about a fifth of global oil supplies before the war.
Iran has since largely taken control of the waterway, forcing a stalemate in its confrontation with the world's most powerful military.
Under the interim deal, the US ended its naval blockade of Iranian ports, and Iran agreed to ensure safe passage of commercial vessels.
However, this week the US accused Iranian forces of attacking three tankers in the area and struck military sites on Iran's southern coast and eastern provinces in response.
While Iran has not claimed responsibility for those attacks, analysts say Iran uses such actions to gain leverage in negotiations.
Iran then attacked US military sites in Gulf countries on Thursday.
The US said its action aimed to keep the strait open and that Iran did not control the waterway.
Iran warned however that the strait would only be reopened on its terms, and any US intervention would draw a "crushing response".
The attacks on the three Qatari and Saudi shipping vessels prompted US President Donald Trump to declare the truce "over" but a US official later said the United States was still committed to finding a resolution with Iran and "technical talks continue".
The New York Times reported that Qatar had been in talks with the US and Iran to de-escalate the crisis.
Prior to this week's attacks, daily tanker traffic had risen to its highest since the war began, averaging 40 ships transiting the strait.
That was still far off the pre-conflict average of 125 to 140 daily sailings.
with DPA
