A record total of 71 journalists were killed in their work around the world last year, including 33 in the Philippines.
The figures were compiled by the New York-based Committee to Protect Journalists in its annual survey.
The 350-page report says the record toll was driven by the mass, election-related killings in the Philippines' Maguindanao province and escalating violence in Somalia.
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The survey, Attacks on the Press in 2009, noted that last year's tally surpassed the previous record of 67 deaths set in 2007. Some 41 fatalities were recorded in 2008.
The survey identified 136 reporters, editors and photojournalists in prison as of 1 December, which is up 11 from 2008.
As in the previous ten years, China jailed the most journalists last year, 24, followed by Iran, Cuba, Eritrea and Burma (Myanmar).
Maziar Bahari, an Iranian-Canadian correspondent for Newsweek, said that more than 100 journalists, bloggers and writers had been arrested in Iran at different periods since last June's disputed presidential polls.
Mr Bahari, who was jailed in Iran in June and released four months later, said more than 65 are still behind bars in Iran.
Most of those were arrested in the Iranian government's post-election crackdown on dissent and the news media.
The survey noted Iraq became less dangerous than in previous years, with four journalists killed last year, the lowest figure since the start of the US-led war in 2003.
But the number of fatalities rose in Somalia, with nine journalists killed last year.
The survey said that throughout the year, Islamist militants of the al-Shabaab militia 'terrorise the media through violence, threats, censorship', forcing many local journalists to flee into exile.
Four journalists were killed in Pakistan, where reporters are hard-pressed to cover areas controlled by Taliban insurgents.
As in previous years, murder is the main cause of death, the CPJ said. At least 51 journalists were murdered.
Three murders were recorded in Russia, two in Mexico and two in Sri Lanka.
CPJ also said it was investigating the deaths of 24 other journalists around the world last year to determine if they were linked to their work.
CPJ Deputy Director Robert Mahoney appealed to UN Secretary General Ban Ki-moon to speak out more forcefully on the issue of freedom of the press.
'I would like the Secretary General to make a more assertive and firm stand in defence of freedom of expression and privacy online and to send out a message to the other UN agencies and to the world that freedom of expression matters,' he said.
