Hunt met his counterpart, Foreign Minister Mohammad Javad Zarif, but neither side took questions from reporters.

It was the first visit to Tehran by a Western foreign minister since the United States withdrew from the multi-nation nuclear deal in May.

Britain is determined to keep Iran in the agreement by finding ways to work around renewed US sanctions.

"The Iran nuclear deal remains a vital component of stability in the Middle East by eliminating the threat of a nuclearised Iran," Hunt said, in a statement issued in London.

"It needs 100-percent compliance though to survive. 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."

Hunt was due to discuss Iran's role in the conflicts in Syria and Yemen, and the ongoing cases of detained British-Iranian dual nationals.

One notable case is that of Nazanin Zaghari-Ratcliffe, who is serving a five-year jail sentence for alleged sedition.

"More than anything, we must see those innocent British-Iranian dual nationals imprisoned in Iran returned to their families in Britain," he said.

"I have just heard too many heartbreaking stories from families who have been forced to endure a terrible separation.

"So 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."

On Yemen, Hunt was to stress concerns at reports that Iran has supplied ballistic missiles and weapons to the Huthi rebels, his ministry said.

burs-er/par