The imposed hijab is a constant source of middle-class debate in Iran, even occasional protest. Michelle Obama in Saudi Arabia. Credit:AP An exile Iranian journalist - who kick-started a popular Facebook page for Iranian women to post photographs of themselves bareheaded - had in recent weeks called for Ms Bishop to refuse to wear the covering. But Ms Bishop said wearing the scarf, which she also covered with a hat, was not an imposition. "As a matter of fact I wear scarves and hats and headgear quite often as part of my everyday wear," she said.

Asked why she had pulled the scarf back to her shoulders for an early hours media conference shortly after arriving, she said it was more comfortable. US first lady Michelle Obama sparked a mini-controversy in January by not covering her hair when attending the funeral in January of late king in Saudi Arabia, in what was quickly - and mistakenly - interpreted as a statement in support of women's rights. Head coverings are not mandatory for foreign women in Saudi Arabia, and both Hillary Clinton and Condoleezza Rice went unveiled for official meetings in oil kingdom during their respective terms as US Secretary of State, wearing a scarf only when visiting a mosque. Yet in Iran a decree following the 1979 religious revolution required all women conceal their hair in public.

In the 1930s under the rule of the Shah in Iran, women had veils torn off. While some religious conservatives in Iran demand strict rules to govern interaction between the sexes, the wearing of the veil is reported to fluctuate across the country and over time.

Many women had visible hair beneath the veil on the street in the capital, and though men and women are segregated at bus stops, a number of couples walked hand-in-hand. Yet there are boundaries. Six friends - three of them unveiled women - who posted a YouTube video dancing on Tehran's rooftops to the Pharrell Williams pop hit Happy last year received a suspended sentence of one year in prison and 91 lashes, according to the BBC. Women have also been targeted in vicious attacks with acid splashed in their face by men accusing them of "bad hijab" - attacks condemned by Dr Rouhani. Ms Bishop is not the first senior female politician to navigate the religious rulings in the Islamic State. Catherine Ashton visited Tehran last March as the European Union high representative for foreign affairs and wrapped her hair in a loose black scarf.

Photographs of Baroness Ashton had previously been digitally altered in Iranian media for "modesty" to conceal her neckline during early rounds of negotiations over Iran's nuclear program. Croatia's foreign affairs minister Vesna Pusic and former New Zealand Prime Minister Helen Clark, now head of the UN Development Program, also visited Tehran in recent times and wore headscarves.