The badly beaten corpses of six young men were found at the weekend at the edge of a river in Democratic Republic of Congo's capital, the United Nations says as it calls on authorities to investigate.
The bodies were found along the banks of the Ndjili River in Kinshasa's Limete commune, the director of the UN Joint Human Rights Office (UNJHRO) in Congo, Jose Maria Aranaz, told Reuters on Monday.
"We are concerned by the finding of six corpses of young men on the river banks and we offer all our support so that a transparent investigation takes place promptly to dispel rumours," Aranaz said.
According to a 2014 UNJHRO report, police executed at least nine men in a 2013-14 anti-gang operation in Kinshasa, dumping some of the bodies into a river.
New York-based group Human Rights Watch said at least 51 people were killed in the operation with some of the bodies dumped in the larger Congo river.
Congolese authorities deny that it conducted the executions or dumped bodies.
Last month, the government announced a fresh crackdown on Kinshasa's notoriously violent street gangs, known as kulunas.
Kinshasa's minister of security, Emmanuel Akweti, told Reuters that authorities will launch an investigation but that they did not yet have any theories to explain the deaths.
Witnesses and a local police officer said the bodies were discovered by fishermen on Sunday morning. They said the men appeared to be in their 20s and their faces and necks were swollen and severely disfigured.
Photographs of two of the bodies seen by Reuters show them lying on the river bank with apparent bruising on their necks and shoulders.
Residents said drowning victims sometimes wash up on the shores, but they have never seen so many bodies at once.