Since April 13, the U.S. Navy has intercepted and diverted 58 merchant ships that were either leaving or attempting to enter Iranian ports, and U.S. forces have “disabled” four other ships that did not comply with U.S. orders, Central Command announced on Saturday.

In public statements, the US and Iran continued to trade threats on Saturday. Iran’s Revolutionary Guards Navy has said any attack on Iranian ships would be met with a “massive attack” on US ships and other US targets in the region. President Trump posted a meme of Iranian warships sinking to the bottom of the ocean.

At least six cargo ships have crossed the Strait of Hormuz since Wednesday, but no tankers, according to data from global ship-tracking firm Marine Traffic. Tracking by the London Stock Exchange Group shows that the number of ships has fallen each day since Monday to an all-time low.

Those intelligence firms can provide an incomplete picture, however, because ships sometimes fake or jam their location signals. Still, the data they’ve collected generally shows how traffic has fallen in recent days, even compared to some other periods during the ceasefire that began on April 7.

There was a new round of clashes in the Straits on Thursday. The United States said it had targeted military sites in Iran after three U.S. fighter jets were attacked in Iran. On Friday, the US military said it had fired on two Iranian-flagged oil tankers trying to reach an Iranian port.

Iran, for its part, said it had attacked US warships on Thursday in response to what it described as US ceasefire violations, including attacks on the country’s southern coast. Iranian forces continued their efforts on Friday, seizing a Chinese-owned oil tanker in the strait.

Mehr news agency quoted a regional governor affiliated with Iran’s security forces as saying that the overnight US attack targeted six boats in the country’s special port, leaving six people missing. There was no US confirmation of the attack.

As tensions between the U.S. and Iran escalated, other countries appeared to be taking steps to address the Strait of Hormuz crisis, which has sent energy prices soaring and jolted markets around the world, with dire consequences for the global economy.

Britain said on Saturday the Royal Navy was deploying a destroyer to the Middle East in what it described as “pre-positioning” for a future mission to secure the Strait of Hormuz. Britain and France have said they are planning a “multinational alliance” to ensure safe passage for ships in the strait after the conflict ends, although there are few details of what that would entail.

According to several ship-tracking intelligence firms, a Qatari gas tanker was trying to pass through Iran’s Strait of Hormuz on Saturday, en route to Pakistan. If the tanker makes it through, it will be the first Qatari natural gas tanker to do so since the start of the war.

It was not clear on Saturday night whether the ship had passed through the Straits of Oman, although the London Stock Exchange Group said that based on its last known position and course, it could have done so. QatarEnergy, the state-owned gas company that operates the tanker, has not commented publicly.

In normal times, about 130 ships passed through the strait every day, carrying, among other things, about a fifth of the world’s oil supply. It is also an important route for ships carrying natural gas, fertilizers and other products.