Why are Iranians protesting and what is the country's hijab law?

Protests have broken out in Iran after people took to the streets to protest the death of a 22-year-old while she was held by authorities for violating the country’s strictly-enforced Islamic dress code.

The young woman, Mahsa Amini, had been picked up by Iran’s morality police for her allegedly wearing her headscarf, or hijab, loose.

Many Iranians, particularly the young, have come to see her death as part of the Islamic Republic’s heavy-handed policing of dissent and the authorities' increasingly violent treatment of young women.

This has led to daring displays of defiance, in the face of beatings and possible arrest. In street protests, some women tore off their mandatory headscarves, demonstratively twirling them in the air, or burned them.

What caused the protests in Iran?

Iran's morality police arrested Ms Amini on September 13 in Tehran, where she was visiting from her hometown in the country's western Kurdish region. She collapsed at a police station and died three days later.

Police detained her over wearing her hijab too loosely. Iran requires women to wear the headscarf in a way that completely covers their hair when in public. Only Afghanistan under Taliban rule now actively enforces a similar law. In comparison, Saudi Arabia dialled back its enforcement over recent years.

The police deny Ms Amini was mistreated and say she died of a heart attack. President Ebrahim Raisi, who will speak at the UN General Assembly on Wednesday, has promised an investigation.

Ms Amini's family says she had no history of heart trouble and that they were prevented from seeing her body before she was buried. The demonstrations erupted after her funeral in the Kurdish city of Saqez on Saturday, and quickly spread to other parts of the country, including Tehran.

How are women treated in Iran?

Iranian women have full access to education, work outside the home and hold public office. But they are required to dress modestly in public, which includes wearing the hijab as well as long, loose-fitting robes. Unmarried men and women are barred from mingling.

The rules, which date back to the days after the 1979 Islamic Revolution, are enforced by the morality police. The force, officially known as the Guidance Patrol, is stationed across public areas. It is made up of men as well as women.

Enforcement was eased under former President Hassan Rouhani, a relative moderate who at one point accused the morality police of being overly aggressive. In 2017, the head of the force said it would no longer arrest women for violating the dress code.

But under Raisi, a hard-liner elected last year, agents of the morality police appear to have been unleashed.

The UN human rights office says young women have been slapped in the face, beaten with batons and shoved into police vehicles in recent months.

How has Iran responded to the protests?

Iranian leaders have vowed to investigate the circumstances of Ms Amini's death while accusing unnamed foreign countries and exiled opposition groups of seizing on it as a pretext to stir up unrest. That's been a common pattern in the protests that erupted in recent years.

Iran's ruling clerics view the United States as a threat to the Islamic Republic and believe the adoption of Western customs undermines society. Khamenei himself has seized on so-called “colour” protests in Europe and elsewhere as foreign interventions — and not as people demonstrating for more rights.

Tensions have been especially high since former US President Donald Trump withdrew from the 2015 nuclear deal with Iran and imposed crippling sanctions.

The Biden administration has been working with European allies for the last two years to revive the accord, but negotiations appear deadlocked as nonproliferation experts warn Iran has enough highly-enriched uranium for a nuclear bomb if it chose to build one. The Islamic Republic insists its programme is peaceful.

The governor of Tehran said on Wednesday that authorities arrested three foreign nationals at protests in the capital, without elaborating. Iranian security forces have arrested at least 25 people, and the governor of the Kurdistan province says three people have been killed by armed groups in unrest linked to the protests, without elaborating.

Activists and human rights groups have blamed Iranian security forces for killing protesters in other demonstrations, like those over gasoline prices in 2019.

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Could the protests bring down Iran's government?

Iran's ruling clerics have weathered several waves of protests going back decades, eventually quashing them with brute force.

The most serious challenge to the clerics' rule was the Green Movement that emerged after the country's disputed presidential election in 2009 and called for far-reaching reforms; millions of Iranians took to the streets.

Authorities responded with a brutal crackdown, with the Revolutionary Guard and the Basij militia opening fire on protesters and launching waves of arrests. Opposition leaders were placed under house arrest.

Among those killed was Neda Agha Soltan, a 27-year-old woman who became an icon of the protest movement after she was shot and bled to death in a video seen by millions on social media.