This year's global theme is 'Keeping Power in Check'
Thirty-three journalists have died around the world so far this year.
The figure comes as World Press Freedom Day is marked.
This includes ten journalists who were killed last month in Afghanistan.
The International Federation of Journalists (IFJ) says unknown gunmen killed Ahmad Shah, a journalist with the BBC Afghan service on April 30th - the same day nine other journalists were killed in a suicide attack in Kabul.
According to media reports, two unknown armed men riding on a motorcycle shot dead Mr Shah while he was on his way home.
It was not immediately clear the reason behind the killing and no group has taken responsibility for the attack.
Earlier in the day, nine journalists lost their lives in a twin blast near the headquarters of the Afghan Intelligence Service. The so-called Islamic State claimed responsibility for the attack.
The Irish secretary of the National Union of Journalists (NUJ), Séamus Dooley, has called for cross-party support on the establishment of a Commission on the Future of the Media in Ireland.
In a letter to the Taoiseach and opposition leaders, Mr Dooley said: "A healthy democracy needs a healthy media.
"That means addressing economic challenges, reforming legal constraints on freedom of expression and looking afresh at media policy, including training and professional development."
This year's global theme is 'Keeping Power in Check: Media, Justice and The Rule of Law'.
It covers issues of media and the transparency of the political process, the independence and media literacy of the judicial system, and the accountability of state institutions towards the public.
It is also examining contemporary challenges of ensuring press freedom online.
The day is used to raise awareness of the importance of freedom of the press - and remind governments of their duty to respect and uphold the right to freedom of expression.