"The Secretary-General is appalled at the continued and increased numbers of attacks against journalists and media workers around the world," Xinhua news agency quoted Stephane Dujarric, the UN chief's spokesman, as saying in a statement on Friday.
The recent killing of Julio Valdivia Rodriguez, a Mexican journalist, is yet another example of the hazardous and difficult conditions in which many journalists work globally, said the statement.
"The Secretary-General condemns all attacks and killings of journalists and calls on the respective authorities to ensure that they are thoroughly investigated and that those responsible are held accountable."
Guterres reiterated his call that free press is essential for peace, justice, sustainable development and human rights.
No democracy can function without press freedom, which is the cornerstone of trust between people and their institutions, said the statement.
"When media workers are targeted, societies as a whole pay a price."
According to the New York-based NGO, Committee to Protest Journalists (CPJ), a total of 17 journalists have been killed so far this year.
Of the 17, 11 were murdered, while the others lost their lives in either crossfire or a dangerous assignment, the CPJ data revealed.