Despite being called a prostitute and a bitch by furious madrasa students, Shinkai Karokhail, one of Afghanistan's 68 MPs with seats constitutionally reserved for women, described what happened on Wednesday morning as "a wonderful occasion".

Afghan Shia women protest against a new family law at a demonstration in Kabul, Afghanistan. (Photograph: Shah Marai/AFP/Getty Images) "It was the first time in the history of Afghanistan that women were aware of their rights," she said. "It was a fantastic statement that women will demand equal rights."

The previous evening one of Afghanistan's most powerful Shia clerics, Mohamad Asif Mohseni, published an order on his personal television station that members of his sect must not allow their wives and daughters to attend the unprecedented and historic demonstration in Kabul against a law the UN says legalises marital rape.

But among the people who tuned in to the broadcast on Tamadon was a young woman called Adila. She lives in a large Shia neighbourhood on the outskirts of Kabul and was enraged by what she saw as an attempt to stop her going to the protest the following morning.

"He had no right to tell us what to do - these are our rights. I knew that this was my responsibility to go to the gathering," she said.

So, fearing her parents would stop her leaving and that Mohseni's followers would prevent her from boarding public buses, she sneaked out of the house in the early hours and walked for nearly three hours.

One of her neighbours, Halima Hosseini, also travelled to the demonstration, and was horrified by the attempts of local men to stop her. "When I left my house there were large numbers of schoolgirls, but they weren't wearing their uniforms and they were going to go to the demonstration," she said. "But these groups of men ordered us to return to our houses and said we were Jewish and slaves of the Christians. Some of them spat in our faces."

While many women appeared to turn back, in the end about 200 turned out for the protest outside Mohseni's imposing mosque and seminary. They were met by hundreds of his enraged supporters who hurled abuse and, according to many of the demonstrators, stones. Not since 1970 has there been a remotely comparable demonstration of women's rights in Afghanistan.

The issue that sparked this week's action was the Shia Family Law, a piece of legislation quietly signed into law by President Hamid Karzai last month after intense pressure from Shia clerics and some of the leaders of the Hazara community - a predominately Shia ethnic minority with enormous electoral clout in a year when Afghanistan will hold presidential elections.

It gives Shia husbands wide-ranging powers over their wives, who are not allowed to leave the house without their husband's permission or to refuse him sex without a medical excuse. The Guardian's revelations about the law brought international outrage, with world leaders, including Barack Obama, lining up to condemn Karzai, who was forced to announce a Ministry of Justice review of the law.

What appears to have spurred the women activists was last week's television broadcast by Mohseni saying Karzai must not bow to western pressure to change the law. "We couldn't agree on whether to have a demonstration until Mohseni said that no one has any right to change the law," said Fatima Hussaini, one of the young activists involved.

"We had to show that he is not the only leader of the Shia and that he has no right to do this to women."

But the demonstration would probably have never happened without the involvement of a more demanding young generation of women activists.

Diana Saqeb, a 27-year-old film-maker who, with half a dozen other young, middle-class women, decided to organise the demonstration, said most women MPs opposed their plan. She said: "Only two of the women MPs in parliament supported us from the beginning. They said it is dangerous, because of the security situation. The Taliban supports this law and when the Taliban supports the law maybe it will attack the women who oppose it."

Soraya Sobrang, 51, an activist at the Afghanistan Independent Human Rights Commission, said the young women's attitude reflects the profound changes that have happened since the US-led toppling of the Taliban regime in 2001.

"Women in Afghanistan now have some education and awareness about their rights, they know that they can demand for their lives and their future."

The question remains whether they have done enough to force Karzai to change the law. A group of women will meet with Karzai in the presidential palace on Tuesday, but Saqeb said she was not optimistic.

"We are very near to the election and Mr Karzai is scared by the mullahs - if he supports us, the mullahs will not support him. But at least now the government and all the people know that women won't be quiet ... we showed that Afghan women are angry and this is our issue too."

Political move to win swing voters

Amid condemnation from human rights groups, President Hamid Karzai last month gave the go ahead for Shia family law to be passed into statute.

The move brought immediate condemnation from the UN, which claims the legislation legalises rape within marriage and bans wives from stepping outside the home without their husband's permission.

Foreign leaders, most notably President Barack Obama, were quick to condemn the Afghan leader's move, which for many bore chilling similarities to the doctrine promoted during the years of Taliban rule in Kabul. Humaira Namati, a member of the upper house of the Afghan parliament, said the law was in fact "worse than during the Taliban".

After seven years as president of Afghanistan, Karzai is increasingly unpopular at home and abroad and he faces an election in August that is expected to be extremely tight.

Leaders of the Hazara minority, which is regarded as the most important bloc of swing voters in the election, are among those who demanded the new law.