Britain has appointed an ambassador to Iran for the first time since 2011 as relations between the countries improve.

Officials on Monday named Nicholas Hopton ambassador, upgrading his diplomatic role. He had previously been serving in a lower position at the British Embassy in Tehran.

Foreign Secretary Boris Johnson said he hopes the decision to name an ambassador will allow the two countries to talk "more directly" about human rights and other concerns including the implementation of a nuclear deal between Iran and world powers.

The decision follows the resumption of direct British Airways flights between London and Tehran last week.

Hopton has previously served as Britain's ambassador to Yemen and Qatar.