Fershteh Ghazi, correspondent for the Tehran daily "Etemad," had to be hospitalized shortly after being released on bail in December 2004. She suffered from poor physical and mental health.
Ma Yalian of China was given an 18-month "re-education through labor" sentence in March 2004 for an article she wrote in which she criticized the Chinese petitioning system.
Sihem Bensedrine, a prominent Tunisian human rights activist, has been subjected to constant harassment and police surveillance.
International PEN says these four women have been targeted for pursuing their right to freedom of expression on the Internet. But they are not alone.
Sarah Wyatt is the program director for PEN's Writers' in Prison Committee.
"The reason we chose the Iranian and Tunisian and Chinese cases was simply that they are really good examples of the kind of suppression that the women writers who use the Internet have faced," Wyatt says.
Wyatt tells RFE/RL that PEN member writers in 100 countries will send protest letters to the Iranian, Chinese, and Tunisian authorities to stop attacks against women who speak out. They are also campaigning for an end to the suppression of cyber-dissidents.
"[PEN members] will also be raising publicity in their own countries, writing articles, having items on their own Internet sites. There is also been lobbying the Internet service providers, so it's basically a lobbying campaign and also a publicity campaign," Wyatt says.
The efforts are part of a yearlong PEN action launched last December in support of cyber-dissidence.
The number of Internet users worldwide has been growing at a fast rate. Chinese media reports that the number of Internet users there has increased by 30 percent in the last year.
Internet usage is also expanding in Iran. Many Iranians, especially young people, turn to the Internet to express themselves.
However, Iranian authorities have been clamping down on those who use the Internet to criticize the establishment.
Last month, the Iranian judiciary sentenced Arash Cigarchi, a young Internet diarist -- or blogger -- to 14 years in prison for expressing his opinions.
Human rights organizations and media groups have expressed concern that Iran is moving to silence freedom of expression on the Internet. During the last eight years, more than 100 independent publications have been shut down in Iran, and the Internet remains the last outlet for freedom of expression in the country.
Wyatt from PEN International says the Internet has become the main platform for dissenting voices in countries where the media in under tight state control.
"One thing we have noticed is that the Internet has become the kind of samizdat of the 21st century. And we are going to use every opportunity that we have in this year -- Women's Day, International Press Freedom Day, the United Nations Commission on Human Rights -- to raise our concerns about this," Wyatt said.
PEN is stepping up its campaign in support of cyber-dissidence ahead of the World Summit on the Information Society (WSIS), due to be held in Tunisia in November. During the summit, government officials, Internet service providers, and NGOs will discuss issues concerning the use of the Internet.