An Iranian appeals court has upheld a 10-year jail sentence against British Council staffer Aras Amiri for "cultural infiltration", the judiciary spokesman has said.

Ms Amiri was "sentenced to 10 years in jail... and she is already serving her term. This verdict has been upheld by the court," spokesman Gholamhossein Esmaili said, quoted by the judiciary's Mizan Online website.

"This person... was identified by us because of her cultural infiltration in society through arts and her widespread activities," he added.

Mizan Online reported Ms Amiri's original sentence on 13 May, saying she had "made a straightforward confession".

At the time, Mr Esmaili said she had been tasked with drawing up and managing cultural "infiltration" projects.

Aras Amiri, a Iranian national who had been living in London, was arrested in 2018 during a trip to visit relatives in Iran.

Iranian authorities shut down the British Council's office in Tehran more than a decade ago for what Mr Esmaili described as "illegal activities".

The appeals verdict comes amid tensions between Iran and US ally Britain over the seizure of oil tankers in recent weeks.

British-Iranian Nazanin Zaghari-Ratcliffe remains in Iranian jail following her 2016 arrest

An Iranian tanker was seized off the British overseas territory of Gibraltar on 4 July on suspicion of shipping oil to Syria in breach of EU sanctions.

That vessel has been released, but Iran continues to hold a British-flagged tanker it seized in the Gulf on 19 July for breaking "international maritime rules".

Tensions had already been strained between the two sides over the fate of British-Iranian mother Nazanin Zaghari-Ratcliffe who was arrested by Iranian authorities in 2016 as she was leaving Tehran.

Ms Zaghari-Ratcliffe, who worked for the Thomson Reuters Foundation, was put on trial and is now serving a five-year jail sentence for allegedly trying to topple the Iranian government.