Oil tanker seizures: what we know
A British-flagged tanker headed into Dubai port in the United Arab Emirates on Saturday after being detained for over two months by Iran, authorities and a tracking website said.
Its seizure was one of several that have ratcheted up tensions this year between Iran and its arch-foe, the United States, and allies of Washington.
Here's what we know about the vessels involved:
Gibraltar security forces aided by British Royal Marines intercepted an Iranian tanker -- the Grace 1 -- off the coast of the UK overseas territory on July 4.
The supertanker was detained on suspicion of shipping its 2.1 million barrels of oil to Syria in breach of European Union sanctions.
The Indian captain of the Panama-flagged vessel later said a military helicopter had landed on its deck before the Marines boarded.
Iran called its seizure an act of "piracy" and warned that the action would not go unanswered.
A Gibraltar court ordered its release on August 15 despite an 11th-hour US legal bid to keep it in detention.
A few days later, it set sail for the eastern Mediterranean flying the Iranian flag and with a new name -- the Adrian Darya.
Iran never officially stated the ship's destination, repeatedly denying it was bound for Syria as it zigzagged eastwards.
The then US national security adviser John Bolton alleged, in a September 6 tweet accompanied by a satellite photo, that the Adrian Darya had arrived at the Syrian port of Tartus.
On September 8, state media in Iran cited foreign ministry spokesman Abbas Mousavi as saying the tanker had berthed on Mediterranean shores and unloaded its cargo, without saying exactly where.
London and Washington accused Iran of having delivered the oil to Syria.
But TankerTrackers said on Twitter that the ship was still "fully laden with oil off the coast of Tartous, Syria".
Iran's Islamic Revolutionary Guard Corps said its forces detained a "foreign tanker" in Gulf waters on July 14 for allegedly smuggling contraband fuel.
The tanker was seized south of the Iranian island of Larak in the strategic Strait of Hormuz, the Guards said.
"With a capacity of two million litres and 12 foreign crew on board, the vessel was en route to deliver contraband fuel received from Iranian boats to foreign ships," it said.
TankerTrackers reported at the time that the Panamanian-flagged MT Riah, used in the strait for fuelling other vessels, had crossed into Iranian waters, and at that point its automatic identification system stopped sending signals.
Revolutionary Guards surrounded the British-flagged Stena Impero with attack boats before rappelling onto the deck of the oil tanker in the Strait of Hormuz on July 19.
The 183-metre (600-foot) ship was impounded at the Iranian port of Bandar Abbas for breaking "international maritime rules" -- by allegedly failing to respond to distress calls and turning off its transponder after hitting a fishing boat.
The seizure of the Swedish-owned vessel came hours after a court in Gibraltar said it was extending the detention of the Grace 1.
Iran said the seizure was a legal measure and that further investigations were required, denying accusations from Britain that it was a tit-for-tat move.
The Stena Bulk company that owns the vessel said seven of it 23 crew members were released on September 4.
Iranian government spokesman Ali Rabiei on September 23 said "the legal process has finished" and the vessel was free to leave.
On Friday, the ship's owner and Hormozgan province's maritime organisation said the vessel had set sail and reached international waters.
The vessel arrived off Dubai shortly after midnight local time (2000 GMT) and halted in the busy waterway overnight according to MarineTraffic.com, a ship tracking website.
It began heading to its anchorage in the emirate on Saturday morning, the website said.
Iran seized another ship on July 31 with seven foreign crew aboard, claiming it was smuggling around 700,000 litres of fuel.
The Guards said the ship was transferred to Bushehr province and handed over to authorities, noting the vessel was en route to deliver fuel to Gulf Arab states.
The vessel's identity and the nationality of its crew were not revealed at the time of its seizure.
On September 7, Iran said its coast guard seized a tugboat allegedly carrying contraband fuel and arrested 12 Filipino crew members.