The police say it is investigating the kidnapping and torture of journalist Joseph Afandy.
Mr Afandy was kidnapped on Friday in Juba by men said to have been driving a numberless car.
He was found on Monday dumped near a graveyard in Juba.
Police spokesman Brig. Daniel Justin says the investigation will include a separate incident in which journalist Joseph Chan was beaten this month and dumped at a graveyard in Jebel suburb in Juba.
He told Eye Radio that those behind the two incidents will be punished.
“There is no person above the law. If anyone is found involved, he will be prosecuted like any other citizen,” he said
Mr Afandy was kidnapped a few weeks after release from detention.
He was arrested in December after writing an article critical of the ruling party, the SPLM.