South Sudanese security forces have temporarily detained at least 10 journalists, activists, and other perceived government critics since the formation of a coalition government between the government and armed opposition at the end of April, the victims and media houses said.

The number of cases nearly doubled in May compared to previous months, civil rights activist Edmund Yakani, who tracks cases of intimidation of media, told The Associated Press.

"It is becoming more tense," Yakani said. "The trend is very disturbing."

Government soldiers roughed up and detained American journalist Justin Lynch and beat his driver at a barracks in Yei town Monday morning when he showed up for a scheduled interview at their base, before releasing him in the afternoon, Lynch told AP. Lynch was reporting on a recent killing of a nun blamed on soldiers.

Early Saturday morning, soldiers stormed a Juba nightclub and prevented controversial South Sudanese rapper Lual D'awol from performing by detaining him and two American journalists, who were there to film D'awol's performance. All three were released.

Three South Sudanese journalists were detained and later released when authorities objected to their work, the journalists or their media houses told AP.

Presidential spokesman Ateny Wek Ateny denied all the incidents. "There are no journalists arrested," he said. "These are just nonsensical stories."

"We are back to the jungle laws," said Union of Journalists of South Sudan chairman Oliver Modi. "They take the journalists and lock the journalists inside for two or three days or a few hours ... then warn at the end of the day not to do what we are doing."

South Sudan dropped 15 places in the Reporters Without Borders world press freedom index from last year. In 2015, at least seven journalists were killed in South Sudan. None of the cases were solved.