Journalists working online are more at risk under repressive regimes that close down newspapers and broadcasters because they "have often been the most nimble at circumventing press restrictions".
Online journalists and bloggers in China, Burma, Vietnam and Iran, who increasingly provide foreign journalists with first-hand local information, are particularly vulnerable says the report, which looks at abuses against journalists for carrying out their work.
While the number of imprisoned journalists in China has decreased from 42 in 2004 to 24 in 2009, most of those jailed are online freelancers, the survey says.
Seventy-one journalists were killed because of their work in 2009 - the highest media death toll ever recorded by the CPJ, a result due in part to the massacre of 31 journalists and media workers in the Philippines in November. Recent figures from the International Press Institute (IPI) suggested the real figure could be as high as 110.
The risk of imprisonment or violent reprisal for their work is on the increase for freelancers and local journalists, because of cuts to media organisations' foreign bureaux.
According to the report for 2009, nine freelance journalists were killed for their work and 60 remained in prison at the end of last year.
"Unable to afford foreign bureaux, more newspapers and magazines are relying on freelancers abroad. These stringers look just as suspicious to dictators and militant groups - and they are distinctly more vulnerable," says Fareed Zakaria, editor of Newsweek International, in a preface to the report.
"In this new environment, local journalists are going to assume added importance—and they will take on greater risk."
Zakaria's colleague, Newsweek reporter Maziar Bahari was recently released from imprisonment in Iran, following his detention in June after the disputed presidential elections in the country.
According to figures from the Committee to Protect Journalists (CPJ) released earlier this month, more journalists are currently imprisoned in Iran than have been held by any other country since 1996, when the committee found 78 imprisonments in Turkey.
Iranian authorities are now holding at least 47 journalists in prison, the CPJ says on its website, with at least 26 journalists jailed in the last two months alone.
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