Iran's foreign minister said a US attempt at "piracy" had failed after a Gibraltar court on Thursday ordered the release of a tanker carrying Iranian oil despite a US detention request.

"Having failed to accomplish its objectives through its #EconomicTerrorism -- including depriving cancer patients of medicine -- the US attempted to abuse the legal system to steal our property on the high seas," Mohammad Javad Zarif tweeted.

"This piracy attempt is indicative of Trump admin's contempt for the law."