USS Abraham Lincoln (CVN 72) conducts US blockade operations related to the Strait of Hormuz on 16 April in the Arabian Sea. The ship's embarked carrier air wing includes eight F-35C stealth fighters, F/A-18 fighter jets, EA-18G electronic attack aircraft, E-2D command and control planes, MH-60 helicopters and CMV-22B Ospreys for logistics support.

• Dual blockades continue: Iran briefly reopened the Strait of Hormuz on Friday but reclosed it Saturday.
• Only 4 ships have crossed the strait since Sunday, compared to dozens during the brief opening, with over 750 commercial vessels now stuck in the Gulf.
• The US has redirected 27 vessels and seized the container ship Touska, while Iran has taken action against ships including shooting incidents with Indian-flagged vessels and a French container ship.

Traffic once again seized up in the Strait of Hormuz as both Tehran and Washington imposed separate blockades, with Iranian vessels continuing to test the US shutdown, tracking data showed on Monday.

Iran announced on Friday that it would reopen the strategic waterway, but the United States did not reciprocate for vessels going to and from Iranian ports.

Dozens of commercial vessels passed through the strait before Iran reclosed the passage on Saturday, later warning that any approaching ship would be treated as a target.

Since Sunday, only four ships have made the crossing in either direction, according to marine tracking firm Kpler.

One of those, the Iranian-flagged Nova Crest that is sanctioned by the US, headed out of the Gulf at around 0400 GMT on Monday, and continued to make its way through the Gulf of Oman, according to Marine Traffic.

However, it is usually when a vessel reaches the Iranian border with Pakistan that the US imposes its blockade.

READ | New Hormuz tensions send oil prices soaring

Iran allowed the sanctioned gas tanker Axon I to enter the Gulf on Monday, destined for the UAE and therefore not subject to the US blockade.

Gas tanker G Summer crossed in the opposite direction on Sunday, having gone into the Gulf earlier in the week, but did not appear to dock at an Iranian port.

It was last detected close to the open sea near the Omani capital of Muscat.

The fourth vessel to cross was the Panama-flagged Starway, owned by China-based firm Hechuang International Group, according to Bloomberg.

The tanker passed westwards through the Iran-approved route at around 0800 GMT on Monday, but made a U-turn around 1200 GMT and was last detected heading back towards the strait.

READ | Iran closes Hormuz Strait again over US blockade with ships mid-transit

Since the start of the blockade, US forces have directed 27 vessels to turn around or return to an Iranian port, the US military said on Monday.

The US appeared to have halted the progress of the sanctioned container ship Shamim on Sunday, which was last detected close to the Iranian port of Chabahar.

Iranian-flagged bulk carrier Artman was also redirected to Chabahar after apparently being intercepted by the US at around 2130 GMT on Sunday.

LPG tanker Raine, also sanctioned, was close to entering open seas on Sunday before performing a U-turn and sailing back towards the strait.

While these vessels seem to have heeded US military demands to change course, US President Donald Trump wrote on his Truth Social platform Monday that the container ship Touska was seized after failing to respond to a warning to stop.

Iran also took action to impose its own closure, with New Delhi summoning the Iranian ambassador on Saturday to lodge a protest over a “shooting incident” involving two Indian-flagged ships in the Strait of Hormuz.

French-flagged container ship CMA CGM Everglade also reported being hit by “an unknown projectile which caused damage to some of the containers”, according to the United Kingdom Maritime Trade Operations (UKMTO).

The brief opening of the waterway had little effect on reducing the number of vessels stuck in the Gulf.

More than 750 commercial vessels transmitted signals from within the Gulf on Sunday, of which around 350 were oil or gas tankers, according to tracking data collated by Bloomberg.