INSI said the incidence of kidnappings and disappearances was rising. (Agencies)
The institute, which organizes safety courses for reporters and monitors risks in trouble spots, said 19 of the dead had lost their lives in Syria.
In addition, at least 18 foreign and 20 Syrian journalists are believed to be missing in the country after being detained or kidnapped there, it said.
The London-based INSI, whose report was officially released in Geneva, did not specify whether these were believed to be held by the Syrian government forces or by Islamist insurgents who are known to be responsible for at least some of the deaths.
Overall the Syrian death total was down from 28 in 2012, but abductions of both foreign and local reporters increased, leading many international news organisations to stop sending journalists to cover the conflict.
INSI, founded in 2003 by major world news organisations, including Reuters, and professional bodies like the Brussels-based International Federation of Journalists, said the Philippines and India were the next most dangerous countries for the media after Syria, with 13 dead each.
In the Philippines, nine were murdered by unknown assailants and four others died while covering the recent typhoon disaster.
In India, the INSI report said, seven journalists were murdered but none of their killings had been thoroughly investigated. Two were killed while covering communal violence and four died in accidents while on assignment.
In Iraq, 11 journalists have died, 10 of them murdered by armed groups and seven of them in the northern city of Mosul. In Pakistan, where bombings and targeted killings are common, nine have died, INSI said.
INSI said the incidence of kidnappings and disappearances was rising.