Deal could see the release of five US-Iranian citizens held by Tehran in exchange for release several billion dollars in frozen Iranian funds held by South Korea

Mohammad Jafar Montazeri is under US and UK punitive measures for prosecution of Mahsa Amini protesters last year

State media quotes Iranian foreign ministry slamming Britain's latest penalties as 'illegal action'

British FM announces ramped up sanctions against Tehran for human rights abuses, says decision on further measures 'is firmly in the hands of the Iranian regime itself'

Treasury Department says the individuals and entities 'facilitated procurement of sensitive and critical parts and technology for key actors' developing ballistic missiles

Washington also targets other Iranians for suspected conspiracies to murder perceived threats against Tehran, which is seeking to avenge 2020 killing of top general

Ship flying flags of Marshall Islands and Panama seen at Iranian port Bandar Abbas; meanwhile, another thought to be carrying Iranian crude disappears from anchorage off Singapore

Opposition group provides UK's The Times with memos showing how powerful unit is involved in key aspects of country's finances; analyst talks of IRGC plan to target global Jewry

Bipartisan group says despite sanctions, Iran's oil exports jumped 35% last year, with proceeds used to sponsor attacks on US citizens

Official says Moscow and Tehran are using US citizens 'as political pawns' and 'bargaining chips' after locking them up 'on false pretenses'