The FCO has significantly toughened its stance on travel to the region in recent days after a top Iranian general was killed in a US airstrike near Baghdad on Friday (3 January).
It is advising against all travel to Iraq, except essential travel to the country’s Kurdistan region, and all but essential travel to Iran.
Any Britons in either Iran are urged to "consider carefully" their need to remain. "If your continued presence is not essential, you should consider leaving," said the FCO.
On Monday afternoon (6 January), the FCO also amended its travel advice for more than a dozen other countries in and around the region.