Iran has sentenced four women's rights activists to six months in jail, including one who was awarded a $75,000 human rights prize in Sweden this year, campaigners said on Wednesday.

It was the latest sign of a clampdown on activists working to change legislation which they say discriminates against women in the Islamic Republic. Iran rejects accusations of bias.

Dozens of activists have been detained over the last two years and several have received mostly suspended prison terms.

The four are also leading figures in a campaign to try and collect one million signatures in support of improving women's rights in Iran. Ardalan this year received Sweden's Olof Palme Prize for her work.

Campaigners say close to 50 of them have been detained since the drive began in 2006, in what Western diplomats see as part of a wider crackdown on dissent. Most were freed within days.

"This is part of a backlash against women's rights activists who demand equal rights in a patriarchal system," campaigner Sussan Tahmasebi said about this week's sentencing by a court.

She said Parvin Ardalan, Maryam Hosseinkhah, Jelveh Javaheri and Nahid Keshavarz would appeal. Their defence lawyers include Shirin Ebadi, Iran's 2003 Nobel Peace Prize laureate.

Ardalan, who won Sweden's Olof Palme Prize in 2007, already faces another six-month jail term and suspended sentences of two and two and half years -- which are being appealed -- on charges of seeking to harm national security.

The 41-year-old campaigner was detained along with 70 other people for a June 2006 demonstration in Tehran square demanding equal rights for women on divorce, inheritance and child custody.

Hosseinkhah, 27, and Javaheri, 30, were also arrested in November and December 2007 for allegedly spreading lies and propaganda against the system over articles written on feminist websites.

"The security strategy of this country is that where there is dissent -- workers, women, bloggers -- they crack down on it right away, because they are afraid of the domino effect," said one Iranian analyst, who asked not to be named.

The activists say women in Iran face institutionalised discrimination that makes them second-class citizens in divorce, inheritance, child custody and other aspects of life.

Iran has exerted mounting pressure on women's rights advocates, and several have been arrested in the past year for calling for changes to Iranian laws or for taking part in public protests.

Iran's new family law, which is yet to be debated by the parliament, has also angered women's rights advocates who say it facilitates polygamy.

Parts of this report is gathered from AFP, AP, and ABC news - Sept. 3, 2008