In July, Michael Christopher and his wife were pulled off a flight to Nairobi, where he had intended to go for medical treatment.
He was held without charge at the National Security Service headquarters before being released at the weekend.
Juba,
A prominent South Sudanese journalist said Monday he had been released after almost six weeks in detention without charge, in a case which prompted alarm from rights groups over press freedom.
"I stayed inside for 39 days and there were no charges put against me... that is why, they decided to release me," said Michael Christopher, chief editor of the Arabic-language daily al-Watan.
In July, Christopher and his wife were pulled off a flight to Nairobi, where he had intended to go for medical treatment.
He was held without charge at the National Security Service headquarters before being released at the weekend.
The United States, international and local rights groups protested at his detention, which Human Rights Watch described as "the latest brazen attack against freedom of the press in South Sudan."
Christopher told AFP he was treated well, and was mainly questioned about comments he had made to Voice of America (VOA) radio about the closure of his newspaper and death threats he had received.
"Those who called me and threatened me with death were not the media authority, but it was individuals and I had opened a legal case against them," said Christopher.
Christopher had invoked the ire of authorities by writing about this year's protests in Sudan.
His newspaper's licence was not renewed in March. HRW said threats to his life had been made in the past.
He said he hopes to re-open his newspaper shortly.
South Sudan ranks 139 out of 180 countries on the Reporters Without Borders (RSF) 2019 global press freedom index.
RSF says years of civil war have weakened the media, and government pressure means self-censorship is rife.
From 2014 to 2017, at least 10 journalists were killed in South Sudan, which only gained independence in 2011.