Iran on Wednesday captured two foreign container ships seeking to exit the Strait of Hormuz and fired at a third one, marking the latest escalation of tensions between Washington and Tehran in the narrow shipping passage, and coming amid a United States naval blockade of Iranian ports which commenced on April 13.

On Monday this week, the US military fired on and then captured the Iranian-flagged container ship Touska close to the Strait of Hormuz in the northern Arabian Sea, as it was en route to the Iranian port of Bandar Abbas. In response, Iran accused the US of “piracy“.

Then, on Wednesday, the US military intercepted at least three Iranian-flagged tankers in ‌Asian waters, the Reuters news agency reported, and was said to be redirecting them away from their positions near India, Malaysia and Sri Lanka.

While a ceasefire between the US and Iran is in place, the attacks, capture, and interceptions of ships by both sides point to an ongoing naval war still playing out in the Strait of Hormuz, through which about 20 percent of global oil and liquefied natural gas (LNG) supplies are shipped during peacetime.

Has Iran’s capture of foreign-flagged ships raised the stakes in the strait even more?

Here’s what we know about how Iran and the US have, step by step, ratcheted up tensions in the strait.

Who controls the Strait of Hormuz?

The Strait of Hormuz runs between Oman on one side and Iran on the other. It links the Gulf to the Gulf of Oman and the Arabian Sea beyond. Oil and gas producers in the Gulf use the channel to ship exports to the rest of the world.

After the US and Israel launched their war on Iran on February 28, Tehran, whose territorial waters extend into the strait, closed the passage to all vessels. On March 4, the Islamic Revolutionary Guard Corps (IRGC) said it was in full control of the strait, and ships would need to get clearance from them to pass through it.

At its narrowest point – just 21 nautical miles (equivalent to about 39km) wide – the strait falls entirely within the territorial waters of Iran and Oman. Iran insists that legally, that gives it – and Oman – the right to regulate traffic through the strait, even though passage through the waterway has historically been free of restrictions.

Through its imposition of controls over who passes through Hormuz, Iran has, for almost eight weeks now, determined which vessels can exit the strait into the Gulf of Oman.

Yet, since the US imposed its naval blockade on April 13, its military has controlled which ships can pass from the Arabian Sea into the Gulf through the Strait of Hormuz.

That scenario has left maritime traffic trapped in a situation where rival militaries control the entry and exit points to the strait, and vessels need approval from both to be able to transit.

Iran’s first Hormuz move

Since the IRGC’s announcement on March 4 of its decision to restrict shipping through the Strait of Hormuz, Iran’s formal position – until recently – was that the waterway was actually closed only to enemy countries, namely the US and Iran.

On March 26, Iran’s Foreign Minister Abbas Araghchi told Iran’s state TV: “The Strait of Hormuz, from our perspective, is not completely closed. It is closed only to enemies. There is no reason to allow the ships of our enemies and their allies to pass.”

Ships from other countries, Iran said, could pass through the strait if they negotiate that passage with the IRGC. Vessels from Malaysia, China, Egypt, South Korea, India and Pakistan passed through the strait through most of March and early April.

In March, the IRGC imposed a “toll booth” system to control vessel traffic through the strait.

Several “vessel transits through the strait have followed a route pre-approved under the IRGC ‘toll booth’ system that requires the ship operators to submit to a vetting scheme”, London-based shipping magazine Lloyd’s List reported on March 26.

According to Lloyd’s, at least two vessels transiting the strait paid the toll fee in yuan, China’s currency.

Amid blocking the strait and reportedly collecting tolls, Iran has continued to send its own ships exporting oil.

Iran’s oil exports through the Strait of Hormuz account for about 80 percent of its total exports. According to Kpler, a trade intelligence firm, Iran exported 1.84 million barrels per day (bpd) of crude oil in March and has shipped 1.71 million bpd so far in April, compared with an average of 1.68 million bpd in 2025.

From March 15 to April 14, it exported 55.22 million barrels of oil. The price per barrel of Iranian oil – across its three major variants, known as Iranian light, Iranian heavy and Forozan blend – has not fallen below $90 per barrel over the past month. On many days, the price has surpassed $100 a barrel.

Even at the conservative estimate of $90 a barrel, Iran will have earned at least $4.97bn over the past month from oil exports.

By contrast, in early February before the war started, Iran was earning about $115m a day from its crude oil exports, or $3.45bn in a month.

In all, this means that Iran has earned 40 percent more from oil exports in the past month than it did each month before the war.

When the US raised the stakes with its naval blockade

The US naval blockade of Iranian ports began at 14:00 GMT on April 13. Since then, US Central Command has said US forces have directed 31 Iran-linked vessels to turn around or return to an Iranian port.

On Monday, the US military fired on and then captured the Iranian-flagged container ship Touska close to the Strait of Hormuz in the northern Arabian Sea, and, a day later, detained another oil tanker sanctioned for transporting Iranian crude oil as it sailed in the Bay of Bengal, which links India and Southeast Asia.

In a post on social media after detaining the Touska, the Pentagon wrote: “As we have made clear, we will pursue global maritime enforcement efforts to disrupt illicit networks and interdict sanctioned vessels providing material support to Iran – anywhere they operate.
International waters are not a refuge for sanctioned vessels.”

How Iran raised the stakes higher

Ever since the US naval blockade of Iranian ports began, Tehran, which was earlier allowing vessels from “friendly” nations to pass through the Strait of Hormuz, has tightened its grip on the strait further.

Justifying the decision not to allow any foreign ships to pass until the US ends its naval blockade on April 19, Iran’s First Vice President Mohammad Reza Aref said the “security of the Strait of Hormuz is not free”.

“One cannot restrict Iran’s oil exports while expecting free security for others,” he wrote in a post on X.

“The choice is clear: either a free oil market for all, or the risk of significant costs for everyone,” he added. “Stability in global fuel prices depends on a guaranteed and lasting end to the economic and military pressure against Iran and its allies.”

The day before, Iran had reportedly fired at two Indian-flagged merchant vessels in the strait. The IRGC said the two ships were attacked because they were “operating without authorisation”, according to state media reports.

Then, on April 22, Iran captured two container ships seeking to exit the Gulf via the Strait of Hormuz after firing on them and another vessel.

Iran’s IRGC said the vessels had violated maritime regulations and entered the strategic waterway without its coordination, according to Iranian state media.

According to Reuters, one of the ships captured was the Panama-flagged MSC Francesca, intercepted on its way to the Sri Lankan port of Hambantota. The vessel was hit by gunfire about eight nautical miles (15km) west of Iran, but it was not damaged and its crew were safe, United Kingdom Maritime Trade Operations (UKMTO) and maritime security sources told Reuters.

The second ship captured was the Greek-owned and Liberia-flagged Epaminondas, which was reportedly fired upon about 20 nautical miles (37km) northwest of Oman, UKMTO and sources told Reuters. The operator of the ship said all crew members were safe. It had been headed towards Gujarat, India.

A Liberia-flagged container ship, Euphoria, was also fired upon in the same area as MSC Francesca but was not damaged and resumed sailing, later reaching Fujairah in the United Arab Emirates, Reuters reported.

Where is all this heading now?

This is the first time Iran has attacked and captured ships since the war began. The ships are also not linked to the US and Israel.

Ali Vaez, the Iran project director for the International Crisis Group think tank, told Al Jazeera that Iran’s capture of ships is not an isolated act but part of a deliberate “tit-for-tat between Iran and the United States”.

“What we are seeing in the Strait of Hormuz is not strategic mastery but mutual brinkmanship, with each side testing the limits of coercion,” he said.

“The danger is that neither believes it can afford to blink, and that makes every incident at sea a potential trigger for wider escalation,” he added.

In a statement on social media on Thursday, Iran’s parliamentary speaker and lead negotiator of the ceasefire talks, Mohammad Bagher Ghalibaf, said a full ceasefire could only work if the US naval blockade is lifted.

He stressed that reopening the Strait of Hormuz would be impossible with such a “flagrant breach of the ceasefire”.

Chris Featherstone, a political scientist at the University of York, told Al Jazeera that in capturing ships, however, Iran has raised tension around any negotiations with the US.

“Historically, the US has been perceived to be more of a legitimate actor, and yet in this war with Iran, the Trump administration has lost a large amount of this perceived legitimacy,” he said.

“This looks like a high-stakes game of poker, with both players staring each other down and waiting for the other to blink. Iran had the opportunity to blink, but in capturing the ships, they put the pressure back on Trump to blink or not,” he added.