ships going through, waiting or diverting journey

Iran’s de facto blockade of the Strait of Hormuz has stoked fears of the gravest disruption to global oil supply in history, as the Middle East conflict stretches into its third week.

The blockade has squeezed shipping traffic to a trickle, with just 21 tankers transiting the route since the war began on Feb. 28, according to S&P Global Market Intelligence, compared to more than 100 ships daily before the conflict.

Most vessels appear to be holding positions outside Hormuz, with thousands of seafarers stranded aboard vessels in the Gulf. Some have explored a pivot to disperse to alternative ports.

Roughly 400 vessels were spotted operating in the Gulf of Oman, as a massive backlog of ships waited near the chokepoint, according to a report from maritime intelligence firm Windward on Sunday.

While Iran has kept a tight grip on the strait, a small number of other ships have made the crossing under varying circumstances, signaling that Tehran is selectively letting through some non-Iranian oil cargo in negotiated safe voyages, according to maritime analysts.

Here’s a look at some of the countries that have had their vessels go through the critical energy route since the war began.

Tehran has largely avoided targeting ships linked to China. Dozens of vessels broadcasting AIS — automatic identification system — destinations referenced Chinese ownership or crew presence while operating in the Gulf, according to Windward.

“This pattern suggests the possibility of an informal access filter, where vessels signaling Chinese ownership or crew may be attempting to indicate neutrality or avoid targeting in the current conflict environment,” Windward analysts said in a report last week.

Beijing was reportedly in talks with Iran to allow crude oil and Qatari liquefied natural gas carriers to pass through the strait. Iran has continued to ship millions of barrels of crude oil to China since the war began.

From March 1 to March 15, a total of 11 China-linked vessels transited through the Strait of Hormuz, according to Lloyd’s List Intelligence, mostly general cargo ships, while tankers operated by mainstream Chinese owners still avoided the route. Earlier this month, Chinese state-owned Cosco Shipping suspended all new bookings for routes to and from ports in the Middle East.

Yet a ship that broadcasts its Chinese affiliation does not always guarantee a safe passage.

One China-owned vessel broadcasting “China Owner” via AIS during transit was struck by shrapnel while sailing from the Middle East Gulf toward Jebel Ali in the United Arab Emirates on March 12, a development that has since deterred further Chinese transits, according to Lloyd’s List Intelligence.

Greek shipowners, run by Athens-based Dynacom Tankers Management, have been among the first mainstream operators to test the route.

The Shenlong, a Liberia-flagged Suezmax tanker managed by Dynacom, transited the strait around March 8, carrying roughly one million barrels of Saudi crude to arrive at Mumbai’s anchorage.

Another oil tanker, the Smyrni, laden with Saudi crude oil, also sailed through the waterway last week and anchored in Mumbai.

It is not yet clear whether Smyrni was allowed safe passage due to its cargo bound for India, said Lloyd’s List Intelligence.

Indian Foreign Minister S. Jaishankar described the country’s direct talks with Tehran as productive. “I am at the moment engaged in talking to them, and my talking has yielded some results,” he told the Financial Times earlier this week. “If it is yielding results for me, I would naturally continue to look at it.”

Two Indian vessels carrying liquefied petroleum gas, or LPG, under the Shipping Corporation of India were also permitted to transit, with one arriving Sunday and a second expected Tuesday.

About 22 vessels carrying crude, LPG, and liquefied natural gas remained anchored in the strait, awaiting confirmation for safe passage, CNBC has learned.

As recently as Monday, a Pakistan-flagged Aframax tanker laden with crude from Abu Dhabi became the first confirmed non-Iranian cargo vessel to transit the chokepoint while broadcasting its location, according to Kpler’s ship-tracking intelligence unit, MarineTraffic.

That shows “select shipments may be receiving negotiated safe passage,” it said.

Turkish authorities also confirmed that one Turkish-owned vessel was permitted to transit after calling at an Iranian port, though 14 additional Turkish-owned vessels remain in the region awaiting clearance.

But the Strait of Hormuz has remained effectively shut to the global energy flow as Tehran continued sporadic attacks on vessels.

Attacks on ships in the Gulf appeared “random” and lacked a pattern, aimed at sowing confusion and disruption rather than targeting specific national profiles or vessel types, maritime analysts said.

At least 16 vessels have been struck in waters near the UAE’s Fujairah port, Iraq’s Khor Al Zubair port and the Gulf of Oman, according to the International Maritime Organization.

Several vessels that were targeted had Western or Gulf-state connections, including links to the U.S., UAE and U.K. through ownership or state registration, according to Windward.

Other affected vessels also included ships arriving from Thailand, Vietnam, and Brazil, indicating “broad targeting of dense commercial shipping lanes rather than a narrow focus on one nationality or operator class,” Windward analysts said.

The attacks have followed no discernible pattern, said Bridget Diakun, senior risk and compliance analyst at Lloyd’s List Intelligence, which “makes things difficult for people trying to plan any transiting, because they can’t work out what the rationale is for one ship getting hit over another,” she said in a phone interview with CNBC.

Shipowners have also scrambled to secure alternative routes, contingency ports or inland transportation networks, setting off a cascade of congestion across the region’s secondary hubs.

When the war began, some 81 container vessels were bound for ports along the Strait of Hormuz, according to Kpler. Since then, 43 have rerouted to other Gulf ports, with the rest diverting from the region entirely.

Cargoes have been redirected to ports outside the strait, notably Fujairah and Khor Fakkan in the UAE, and Oman’s Sohar, before being moved by truck to their destinations.

— CNBC’s Seema Mody contributed to this report.