French soldiers on patrol pass ethnic Hutu troops from the Rwandan government forces 27 June 1994, near Gisenyie, about 10kms from the border with Zaire.
An increasing number of people have been forcibly disappeared or have been reported missing in Rwanda since March 2014, Human Rights Watch said in a report Friday, blaming the national army for some of the cases.
The US-based rights group said it had documented "detailed accounts of 14 people who have been forcibly disappeared or who have been reported missing" in Rubavu, a district in the Rwanda's Western Province, close to the border with the Democratic Republic of Congo.
It also said there were "indications of involvement of state agents in the disappearances".
"Enforced disappearances are a heinous crime, not least because of the anguish and suffering they cause to family and friends," said Daniel Bekele, Africa director at Human Rights Watch.
"Rwandan police and judicial authorities have strict and absolute obligations to thoroughly investigate any case of enforced disappearance," he said, adding that Rwandan officials told HRW that they were investigating the cases "but have not provided any information on the progress or results of their investigations."
According to HRW, some of those detained may have been suspected of links to the Democratic Forces for the Liberation of Rwanda (FDLR), Rwandan Hutu rebels who include the perpetrators of the 1994 genocide in their ranks and who are based in the forests of neighbouring DR Congo.
"Since 2010, Human Rights Watch has documented a number of cases of people accused of being FDLR members or collaborators, or charged with state security offences, and who were detained incommunicado by the military and forced to confess to crimes, or implicate others, sometimes under torture," the statement said.
The allegations come as Rwanda continues to mark the 20th anniversary of the genocide, but also amid mounting criticism of the alleged suppression of political dissent by Rwanda's strongman President Paul Kagame.
Kagame's regime has also been accused of assassinating opposition figures and dissidents who are based abroad, charges the authorities in Kigali have strongly denied.