The Alliance for Media Organisations highlighted the murders of at least two leading editors and media workers.
'Killers not found' was marked on the portraits of Lasantha Wickramatunga, the outspoken editor of the Sunday Leader and Dharmaratnam Sivaram, the editor of the TamilNet website.
Sivaram was killed in 2005 while Wickramatunga died of severe head injuries in 2009 after bring attacked by an unknown group.
Protesters shouted slogans like "resist suppression of media" and said most of the prominent attacks against journalists had taken place during the month of January.
Prageeth Eknaligoda the last of the media workers to disappear out of trace was a cartoonist/columnist. His whereabouts are not known since January of 2010.
The international media watchdog - Committee to Protect Journalists (CPJ) - has termed Sri Lanka as one of the most dangerous places to function as journalists.
According to activists, at least 16 journalists or media workers were killed in the country since 2000. Many more have fled the country due to threats.
