Iran is set to release the British-flagged tanker Stena Impero which it detained more than two months ago.

The ship's seizure in the Strait of Hormuz in July came two weeks after an Iranian tanker was detained off the coast of Gibraltar, Sky News says.

An Iranian government spokesman said all legal steps had been completed for Stena Impero's release but he did not confirm a date when it would be freed.

"The legal work for the oil tanker is over and the oil tanker can move, and the decisions indicate the end of the detention," the spokesman said.

The ship has not turned on its satellite-tracking beacon in 58 days nor has there been any sign that it has left its position off the Iranian coast near the port city of Bandar Abbas.

Stena Bulk, the ship's Swedish owners, is yet to comment publicly about the ship's departure.

Earlier this month, Iran released seven of the 23 crew members on board Stena Impero.