Hundreds of journalists and media rights activists have protested to demand Sri Lanka's government start a fresh investigation into the abduction and killing of a prominent ethnic Tamil journalist 11 years ago, during the country's civil war.

Those demonstrating in front of Colombo's main railroad station on Friday said Dharmeratnam Sivaram was targeted because of uncompromising coverage of political and military matters.

Media rights activist Lasantha Ruhunage said law enforcement authorities have failed to find the killers and should start a fresh investigation and bring the culprits before law.

Sivaram was found dead on April 29, 2005, in the capital, Colombo, after being abducted the previous evening.

Scores of journalists and media workers were killed during the country's 30-year civil war which ended in 2009.