Journalists Mzilikazi Wa Afrika and Stephan Hofstatter are being intimidated, the Sunday Times reported.
Wa Afrika said he was tipped-off by sources close to South Africa's intelligence bodies that he was "a marked man" and "hitmen have been hired".
The newspaper had provided extra security for the two men after it became aware, earlier this year, that their movements and their telephone calls were being "monitored".
Wa Afrika said in a sworn statement last week that he had experienced two threatening encounters and had been warned in December that he would be killed by hitmen wearing SAPS uniforms.
Editor Ray Hartley said the newspaper took the threats seriously.
"...It seems that there are some in the security services who are taking this intimidation to a more sinister and dangerous level while political leaders turn a blind eye."
SA National Editors' Forum (Sanef) chairperson, Mondli Makhanya, said: "Intimidatory tactics such as these belong in jackboot banana republics and not in a constitutional democracy such as ours".
Wonder how long before this becomes a daily occurence... YOU SPEAK AGAINST THE ANC? BOOM... DEAD.
I'm surprised your post has not been deleted
Wonder who is behind this. Oh, wait, you don't need a few years of investigation, it's David Mabuza, the untouchable.