UNESCO says the killing of Ahmad Mohamed al-Mousa was "unacceptable tragedy"
The United Nations agency responsible for defending the freedom of the media has denounced the murder of a Syrian journalist.
Ahmad Mohamed al-Mousa was working for an organisation reporting on human rights abuses in an area of the country controlled by the Islamic State in Iraq and the Levant (ISIL).
"It is an unacceptable tragedy for society as a whole when those who contribute to public debate and to the free flow of information are made to pay with their lives for doing their important work," UNESCO Director-General Irina Bokova said.
Mr al-Mousa was killed last week in Idlib, northwest Syria.
Mr al-Mousa, who was murdered by unidentified masked men, was a reporter for the citizen journalist collective Raqqa is Being Slaughtered Silently (RBSS).
The organisation focuses on human rights violations in the region.
His murder follows that of RBSS co-founder and executive director Ibrahim Abdel Qader - who was killed along with Fares Hammadi, head of production at Eye on the Homeland, a Syrian media collective, in Sanliurfa, Turkey, last month.