British Foreign Secretary Jeremy Hunt visited Iran on Monday for talks on issues including the future of the 2015 nuclear deal.

Hunt was due to discuss Iran's role in the conflicts in Syria and Yemen, and press Iran on its human rights record, calling for the immediate release of detained British-Iranian dual nationals where there are humanitarian grounds to do so.

Hunt's office said he would meet Iranian Foreign Minister Mohammad Javad Zarif and would stress that the UK is committed to the nuclear deal as long as Iran sticks to its terms.

"The Iran nuclear deal remains a vital component of stability in the Middle East by eliminating the threat of a nuclearized Iran. It needs 100 percent compliance though to survive," Hunt said in a statement ahead of the visit.

"We will stick to our side of the bargain as long as Iran does. But we also need to see an end to destabilising activity by Iran in the rest of the region if we are going to tackle the root causes of the challenges the region faces."

In May, US President Donald Trump abandoned the Iran nuclear deal, which was negotiated with five other world powers during former president Barack Obama's administration.

Britain and its European allies responded with dismay to Trump's decision to pull out of the deal, the 2015 Joint Comprehensive Plan of Action (known as JCPOA), that relieved sanctions on Teheran in return for an end to Iran's military nuclear ambitions.

Earlier this month the US restored sanctions targeting Iran's oil, banking and transportation sectors.

Trump said the Iranian regime was not doing enough to halt its nuclear program or its support for terrorism and groups fighting in Syria.

Iran is also backing Shia Houthi rebels fighting the Saudi-backed government forces in the Yemen civil war.

Hunt is the first European foreign minister to visit Iran since the US pulled out of the nuclear deal.

The foreign secretary was expected to make a personal appeal for the immediate release of the Iranian-British dual-national Nazanin Zaghari-Ratcliffe on humanitarian grounds.

Zaghari-Ratcliffe, a British-Iranian mother who works for the Thomson Reuters Foundation, was arrested at Teheran's Imam Khomeini International Airport in April 2016 and later sentenced to five years in jail after being accused of spying, a charge she vehemently denies.

"I arrive in Iran with a clear message for the country's leaders: putting innocent people in prison cannot and must not be used as a tool of diplomatic leverage," Hunt said.

Speaking during a tour of Teehran's Grand Bazaar on Monday morning, Hunt said: "This is part of the world that is quite frankly a tinderbox. We want to move to peace in Yemen – that is our number one priority at the moment. We also have the case of Nazanin Zaghari-Ratcliffe and other dual nationals who are in prison who should not be. We want to get them home, so all these things have to be discussed."