This is what you should know about trapped ships

The Supreme Court of Gibraltar on Thursday allowed an Iranian oil tanker held since early July to leave despite a US request to extend the detention on suspicion of seeking to deliver its cargo to Syria.

Gibraltar Prime Minister Fabian Picardo said he had received a written promise from Tehran not to send the 2.1 million barrels of oil to Syria, which is under European embargo.

The detention of tankers in recent weeks has fueled tensions between Iran and the United States and its allies.

Here's what we know about her:

Grace 1:
On July 4, Gibraltar police and customs intercepted British territory in southernmost Spain, the Iranian tanker Grace 1, with the help of a detachment from the British Royal Navy.

The Gibraltar government and the United States said at the time that the 330-meter-long vessel was bound for Syria “in violation” of sanctions approved by the European Union.

The captain of the Indian ship said that a military helicopter landed on the bridge before the Royal Navy stepped up. Iran has described the detention of the ship as "naval piracy" and warned it would retaliate.

Tehran did not officially disclose the destination of the tanker, but denied that it was heading to Syria.

On Thursday, Chief Justice Gibraltar Judge Anthony Dudley decided that "the ship is no longer in detention."

MT Wind
On July 14, the Iranian Revolutionary Guards intercepted a "foreign tanker" accused of transporting smuggled oil, south of the Iranian island of Larak, in the strategic Strait of Hormuz.

The Revolutionary Guards said the tanker, which has a capacity of "2 million liters with 12 foreign crew members, was on its way to deliver the smuggled oil it received from Iranian boats to foreign ships."

Tanker Trackers, which specializes in tracking oil shipments, said it lost the MTM flag, which was flying the Panamanian flag on July 14, from the moment it entered Iranian waters.

Stina Ambro
On July 19, the Iranian Revolutionary Guards besieged the tanker Stena Ambro before boarding it in the Strait of Hormuz.

The 183-meter vessel was seized and directed to the Iranian port of Bandar Abbas for "non-compliance with international maritime law."

She was accused of ignoring distress calls and turning off the transmitter and receiver after hitting a fishing boat.

The British-flagged tanker, owned by a Swedish national, was staffed by a crew of 23, including 18 Indians, the rest from the Philippines, Latvia and Russia.

London is demanding that Tehran quickly release "Stena Ambro," considering it being held illegally. But Iran maintains that its detention is a legal measure and that the investigation is necessary, and denies that it is in retaliation, as reported by London.

An unidentified tanker
Tehran detained a third oil tanker on July 31 with seven foreign crew on board, saying it was carrying 700,000 liters of smuggled fuel.

The Revolutionary Guards said they had taken the ship to the southern port of Bushehr and handed over to the authorities the ship that was on its way to deliver crude oil to Gulf states.