Media watchdogs are voicing concern about curbs on press freedom.
The conviction has been described as an "outrage"
The offices of Jamii Forums were raided by police on December 14, and multiple other staff were questioned.
The detentions come less than a week after the offices of a Somali newspaper were raided and its editor held for three days.
"If anybody among them (journalists) does not know that this country has killed people, we will demonstrate it one day, one time" - Kiir