Tracking the ships crossing the Strait of Hormuz

The first vessel has crossed the Strait of Hormuz after the US imposed a military blockade of Iran's ports, according to ship tracking data.

US Central Command announced the blockade of "all maritime traffic entering and exiting Iranian ports" on Sunday night, but said it will "not impede" vessels transiting the strait travelling to or from other countries.

The container ship Paya Lebar is en route to Dubai in the United Arab Emirates from India.

Earlier on Monday four vessels crossed the strait in the hours before the blockade came into force at 14:00 GMT (15:00 BST).

All four were tankers carrying either oil, gas or chemicals, according to tracking data provided by MarineTraffic.

One of the ships, the Auroura, is on a US sanctions list for transporting Iranian petroleum products.

A second vessel, the NV Sunshine, is suspected by the US-based group United Against Nuclear Iran of helping transport Iranian petroleum products.

The Strait of Hormuz has become a focal point of the US-Israel war with Iran after Tehran effectively choked off one of the world's most important shipping lanes.

President Donald Trump says the US blockade is in response to Iran "knowingly failing" to reopen the strait.

He also warns the US Navy will "blow to hell" any Iranians that attack them and will take action against any ship found paying transit tolls to Iran.

The disruption to shipping since the conflict began six weeks ago has sent shock waves across the global economy, destabilising energy prices and exposing just how reliant international supply chains are on the channel that connects the Gulf with the Indian Ocean.

Jakob Larsen from the Baltic and International Maritime Council, which represents shipowners, told BBC Verify he is concerned about the "risk of further escalation to involve direct attacks on ships" with the introduction of the US blockade.

BBC Verify has tracked 23 vessels transiting the Strait of Hormuz since the breakdown of ceasefire talks between Iran and the US early on Saturday morning.

At least 16 of these are linked to an Iranian port, fly under the Iranian flag or have been sanctioned for links to Iran.

An average of 138 ships passed through the strait each day before the conflict started on 28 February, according to the Joint Maritime Information Centre.

If crossings for ships not linked to Iran do resume at a greater pace, experts stranded tankers that are fully loaded with cargo will be the priority.

"You've had nearly 800 ships stuck in there for several weeks. Most of them are now loaded with cargo so the priority is going to be to get them out," said Richard Meade, editor-in-chief of Lloyd's List

BBC Verify's analysis of the paths taken by the ships shows them taking a northern route through the strait close to Iran's coastline, within its territorial waters.