A picture taken on July 21, 2019, shows Iranian Revolutionary Guards patrolling around the British-flagged tanker Stena Impero as it's anchored off the Iranian port city of Bandar Abbas. - Iran warned Sunday that the fate of a UK-flagged tanker it seized in the Gulf depends on an investigation, as Britain said it was considering options in response to the standoff. Authorities impounded the Stena Impero with 23 crew members aboard off the port of Bandar Abbas after the Islamic Revolutionary Guard Corps seized it Friday in the highly sensitive Strait of Hormuz. (Photo by Hasan Shirvani / MIZAN NEWS AGENCY / AFP) (Photo credit should read HASAN SHIRVANI/AFP/Getty Images)

The head of the shipping firm that owns the British-flagged oil tanker held by Iran since July has said it is still in Iranian waters, a day after Tehran said the vessel was free to move.

Erik Hanell who is the Chief Executive of Swedish company Stena Bulk, told the Associated Press: “We know nothing as to why she is still there.”

On Monday, Iranian government spokesman Ali Rabiei told journalists that legal proceedings against the Stena Impero had ended. The tanker has been kept in the

Iranian port of Bandar Abbas since July 19.

“Based on a friendly approach that allows forgiving mistakes, ground for freedom of the tanker has been paved and it can move,” Mr Rabiei said.

Iran seized the tanker in the Strait of Hormuz, the narrow mouth of the Persian Gulf through which 20% of the world’s oil passes.

The raid saw commandos drop on to the ship from a helicopter, carrying assault rifles, with dramatic images later replayed on state television.

Earlier this month, Iran released seven of the ship’s crew members, but 16 remain on board.

The seizure came after authorities in Gibraltar seized an Iranian tanker carrying 130 million dollars (£104 million) in crude oil on suspicion of it breaking European Union sanctions on Syria.

Gibraltar later released the tanker, then called the Grace 1, after it said Iran had promised the ship would not go to Syria.

The ship, renamed the Adrian Darya 1, now sits off the Syrian coast, angering Britain.

Iran has not said who purchased its 2.1 million barrels of crude oil.

The ship seizures came after months of heightened tensions in the Persian Gulf, sparked by President Donald Trump’s decision over a year ago to withdraw from Iran’s nuclear deal with world powers and impose crippling sanctions on its vital oil trade.

Iran since has begun breaking terms of the deal.