The US Department of Justice has made a last-minute request to the authorities in Gibraltar to halt the release of a seized Iranian supertanker.

Grace 1, carrying Iranian oil, was stopped by Royal Marines on 4 July, triggering a standoff with Tehran.

The vessel was due to be released, after Gibraltar's attorney general indicated there would be no further order for its detention.

But the US request will be considered, with a court hearing set for 15:00 BST.

Gibraltar said the US application is based on a "number of allegations which are now being considered".

The UK Foreign Office said it was unable to comment on the US request.

BBC World affairs correspondent Jonathan Marcus said the UK had been hoping the release of Grace 1 would clear the way for the eventual freeing by the Iranians of the Stena Impero, a British-flagged vessel they seized in the Gulf.

A spokesman for Gibraltar's government also confirmed that police proceedings against all four members of the crew, including the captain - an Indian national - had ended.

The crew's legal team told the BBC that police had said this was due to actions by the Iranian government, and that it was no longer in the public interest to proceed.