Masih Alinejad, a US-based Iranian journalist, started a social media campaign in 2014 encouraging women in Iran to share self-portraits without the Islamic veil, which she then shares on her Facebook page, "My Stealthy Freedom".
She said campaigners had continued to send her pictures and videos after Tehran's Revolutionary Court said on Monday that they could face up to 10 years in prison.
"Today I have received lots of videos from inside Iran. And women in these videos are braver and angrier than before," she told the Thomson Reuters Foundation in emailed comments.
She said Iran's government was "scared of women practising civil disobedience and engaging in peaceful protest".
Many Muslim women cover their heads in public with the hijab as a sign of modesty, although some critics see it as a sign of female oppression.
Under Iran's Islamic law, imposed after the 1979 revolution, women are obliged to cover their hair in public. Violators are publicly admonished, fined or arrested.
Those in breach of the law can face a prison sentence of up to two months, according to rights group Amnesty International, which says women and girls are regularly stopped in the street by morality police and vigilantes.
The Tehran subway company has also promised stricter enforcement of hijab rules on their trains.
Iranian police have encouraged citizens to spy on one another. Those who are called in by the vice-squad to designated stations receive jail sentences or cash fines. There have also been reports about individuals receiving lashes on some occasions.
In Tehran, 300,000 text messages were sent to women and many cars were detained for weeks, according to Police Chief Hossein Ashtari.
The government has instituted many other "over-exaggerated and often irrational moves against women," according to Radio Farda.
Iran's Supreme Leader Ayatollah Ali Khamenei has told law enforcement to ignore "opposition by certain individuals and the media hype" against the harsh treatment of woman.
The Islamic republic has also ordered tailors not to design cloaks that would reveal women's legs, although they all wear pants underneath anyways as a rule.
Sharing pictures of the harsh treatment of women in Iran on social media platforms abroad can land you up to ten years in jail on charges of cooperating with foreigners, threatened the chairman of the revolutionary court in Tehran, Mousa Ghazanfarabadi.
Tehran deems Alinejad to be acting on behalf of the United States.
"All those women who send the video footage of removing their hijab to her will be sentenced to between one to 10 years of jail," Musa Ghazanfarabadi told the semi-official Fars news agency.
The Iran embassy in London did not immediately respond to a request for additional comment.
Iran's laws are written in a "very broad and vague manner" and that can be used by courts to increase penalties for women's rights protesters, said Raha Bahreini, an Iran researcher with Amnesty.
"This is a distressing pattern which shows that they want to increase their crackdown on this peaceful movement and they want to punish those who dare to defy compulsory veiling laws with very severe penalties," she said.
Iranians on social media have a few different theories as to why the government has suddenly increased enforcement of the hijab rule. Some believe that it's a show of force as Iran is preparing to make sure it doesn't appear weak when it eventually acedes to US demands on the nuclear deal.
Others believe that the government is still staying defiant against the West, but is showing harsh force against Iranian women to prevent citizens from rioting due to economic sanctions.
Another fairly popular explanation is that the ruling clerics are scared that if they give up on the hijab issue, then people may gain the courage to protest or change other issues, such as their political power.
Last year, Iranian women, branded the “Girls of Revolution Street” on social media, protested being compelled to wear a hijab by removing their headscarves, according to Radio Farda.
At least 39 women were arrested last year in connection with anti-hijab protests, according to Amnesty.
Before the protests, women arrested for appearing in public without "proper covering" were quickly released or recieved short jail sentences and small fines. Last year, Narges Hosseini, the second woman to take off her headscarf and wave it on top of an electric box in public, received a sentence of 24 months in prison, although 21 months of the verdict were suspended.
“I had prepared myself for any conviction before removing my headscarf, but I did not expect to be condemned to prison and paying a huge fine. I was shocked by the verdict,” said Hosseini.