Iran reportedly stopped an oil shipment to Greece over the weekend. When Greek tankers arrived at an Iranian port they were refused their 500,000 barrel oil cargo, said semi-official Iranian news agency Fars.

However an Iranian oil official has denied the action, while the Greek oil refiner Hellenic Petroleum which was due to receive the shipment said its supplies have all been processed normally, according to other reports.

Last week Iran apparently banned oil deliveries to the UK and France, which has been seen as retaliation for the EU’s oil embargo on Iran, meant to start over the summer.