Iran has arrested a British-Iranian on suspicion of links to the UK intelligence service, the Tehran prosecutor told Iranian media on Tuesday.

"The accused, who was arrested in Tehran last week, was active in the field of the Iranian economy, and was linked to the British espionage service," the Mizan news agency quoted Abbas Jafari Dolatabadi as saying.

He did not give the name or gender of the accused.

Three other dual-nationals arrested over the past year -- American, British and Canadian -- are currently awaiting trial. 

Dolatabadi recalled warnings by supreme leader Ayatollah Ali Khamenei that Western governments would seek to "infiltrate" the country in the wake of last year's nuclear deal.

Iran does not recognise dual nationality and treats those arrested as Iranian citizens only.