The New York-based Committee to Protect Journalists (CPJ) said in its annual report, released at a Tokyo news conference, that freelancers and local reporters faced more risk of attack from dictators, repressive governments and militant groups because they did not have media organizations to back them.
But blogs, social networking sites and other new forms of media have also helped fight censorship, although there were exceptions such as in China.
E-mail alerts, Facebook petitions and blog posts helped raise the visibility of imprisoned journalists in Iran after crackdowns on the media in the aftermath of a disputed presidential election last June, CPJ said.
That international pressure helped in the release of high-profile journalists such as Newsweek correspondent Maziar Bahari and freelancer Roxana Saberi.
"When you attain a critical mass, when you get the blogosphere buzzing or you get people retweeting, or you get people signing petitions and passing around information on social networking, then you get the mainstream media covering it and you can build a groundswell and you can affect governments," Joel Simon, CPJ executive director, said at the news conference.
But advocates of media freedom faced obstacles in China, where CPJ said tight online censorship hindered access to information on infringements.
"Censorship technology is growing and becoming so sophisticated in China, that makes it even harder for local people who are interested in getting a word out about these imprisonments or about other infringements, to contact us, to contact their counterparts overseas, to contact the media," Madeline Earp, of CPJ's Asia program, told the news conference.
Google Inc., the world's biggest search engine provider, threatened last month to shut its Chinese portal and pull out from China, citing cyber attacks and tightening censorship.
But Earp said bloggers in China had not given up on working around censorship by information authorities.
"It's always a moving target -- what are they going to come up with next to try to stop the conversation," she said.
"But it's the authorities who are ... aggressive. And it's the people on the ground who are then reacting to that and thinking, okay, we still want to get the truth out, what's our next move going to be?"