Two women in Iran who went into a store while not fully covering their hair had yoghurt thrown over them by a man, in an incident captured on video.
CCTV footage showing the "yoghurt attack", believed to have taken place in the city of Shandiz in northeast Iran, has been spreading on social media.
Iran's President Ebrahim Raisi insisted that the hijab is the law in the country, in response to the widely shared clip.
It shows a man in a chequered shirt getting increasingly animated as he speaks to one of the women.
He is then seen grabbing a pot of what is believed to be yoghurt and throwing it over the pair before being confronted by another man and pushed out of the store.
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Following the incident, the two women have been arrested for not covering their hair, according to judicial authorities.
The man has also been arrested for insulting the women, public disorder and "unconventional promotion of virtue".
Authorities said the owner of the dairy shop, who confronted the attacker, had also been warned.
Reports on social media showed his shop had been shut, although he was quoted by a local news agency as saying he had been allowed to reopen and was due to "give explanations" to a court.
President Raisi said: "If some people say they don't believe [in the hijab]... it's good to use persuasion...
"But the important point is that there is a legal requirement... and the hijab is today a legal matter."
Women in Iran had already been warned by the regime's judiciary chief that they will be prosecuted "without mercy" if they are seen in public without a veil.
Following protests in recent months, Gholamhossein Mohseni Ejei said on Saturday: "Unveiling is tantamount to enmity with [our] values.
"Those who commit such anomalous acts will be punished and will be prosecuted without mercy."
Iran has been rocked by huge waves of protests following the death of Mahsa Amini in September.
The 22-year-old Kurdish-Iranian woman died while in the custody of Iran's morality police.