The bodies of two prominent South Sudan activists were dumped in Achwa River in Nimule after being killed, intelligence sources said.
The sources said the two critics of President Salva Kiir's government Mr. Dong Samuel, a lawyer and human rights defender and opposition politician Izbon Agrey Idri corpses were transported from Juba to Nimule where they were dumped in the river.
"They were taken the same day they got killed in Juba," one intelligence source told Africa Review.
He added that the river was a notorious dumping site of people executed by the state agents.
"When they dump these dead bodies there, they tie them with stones so that the corpses will not float in the water," he said.
Africa Review was unable to independently verify the claims.
The UN Panel of Experts on South Sudan said last week the two activists were killed in Luri in Juba by the National Security Service
(NSS) under directives from their boss General Akol Koor Kuc.
"It is highly probable that opposition member Aggrey Idri and human rights lawyer Dong Samuel Luak were kidnapped in Kenya where they had fled, taken to the capital of Juba, and slain on orders of Lt.
General Akol Koor Kuc, director of the service's Internal Security Bureau," the report by UN says. The experts said the two were killed on January 30, 2017, a week after they were abducted from Nairobi Kenya.
The UN further said NSS was operating outside the law in the war-torn state to kill, arrest, torture and apprehend government critics whether activists, journalists and opposition dissidents.
South Sudan Information Minister Michael Makuei Leuth denied the government was responsible for the kidnapping and killing of the two activists.
Juba further called for investigation to the death of the two prominent activists to start in Kenya where they were kidnapped.
Kenya has maintained it was not aware of the incident.
Amnesty International and Human Rights Watch have condemned the killing of the two activists and called upon South Sudan government to uphold the rule of law and respect its constitution.
They accused Kenya of colluding with South Sudan in the apparent abduction in Nairobi in 2017.
Human Rights Watch and Amnesty International noted in a joint statement that a United Nations panel of experts has now concluded that the two South Sudanese were likely executed in South Sudan on January 30, 2017.
Dong and Aggrey had apparently been kidnapped on the streets of Nairobi on January 23 and 24, 2017 respectively.
"The men's disappearance is widely viewed to be the result of collusion between South Sudan and Kenya," HRW and Amnesty said.
"Kenya and South Sudan failed miserably in their duty of care toward Dong and Aggrey," said Seif Magango, Amnesty's deputy director for East Africa, the Horn and Great Lakes Region.
"Dong was registered as a refugee in Kenya and for him to be kidnapped in Kenya and taken to South Sudan to be executed, is appalling."
South Sudan's main opposition leader, Riek Machar, has also denounced the execution of the duo.
Dr Machar described the killing as a crime against humanity and asked the international community and human rights watchdogs to refer the case to the Hague-based International Criminal Court (ICC).
Human rights abuses have become common in South Sudan especially after the outbreak of war in December 2013.
President Salva Kiir has been under intense pressure from the international community and South Sudan donor countries of United States, United Kingdom, and Norway to stop impunity against government critics.
UN says the unlawful killing or execution of government critics by the NSS poses a significant threat to the September's shaky peace agreement.