A South Sudanese journalist, Peter Julius Moi, working with the independent New Nation newspaper in Juba, was shot dead while leaving his office late on Wednesday. His colleagues, however, did not say anything about who could be behind the killing.
A Reuters reporter saw his body on Thursday lying in the field where he was shot.
The killing comes just days after President Salva Kiir issued a warning to journalists.
"The freedom of press does not mean that you work against your country. And if anybody among them does not know this country has killed people, we will demonstrate it one day on them," Kiir told a news conference on Sunday, without elaborating.
Police and government officials were not available immediately for comment. Kiir declined to sign a peace agreement proposed by mediators on Monday to end the country's 20-month conflict, saying he had some reservations about the pact and asking for an extra two weeks.
Tom Rhodes, the east Africa representative for press freedom group, Committee to Protect Journalists, told Reuters the killing would make the media's work harder at a time the public needs information on the search for a peace settlement.
"A very foreboding sign, the journalist was killed just three days after President Salva Kiir threatened to target journalists before departing for peace talks in Addis Ababa," Rhodes said.
"It is still too early to tell whether there is a link but this tragedy will certainly cast a pall over independent reporting in the country as South Sudanese journalists are increasingly forced to self-censor as a means of survival."