Open this photo in gallery:ASSOCIATED PRESS

A Rwanda Patriotic Front (RPF) rebel walks by the the site of a April 6 plane crash which killed Rwanda's President Juvenal Habyarimana in this May 23, 1994 file photo in Kigali.

JEAN MARC BOUJOU/ASSOCIATED PRESS

GEOFFREY YORK AND JUDI REVER

JOHANNESBURG AND MONTREAL

In a new twist to the unsolved mystery of the assassination that triggered the Rwandan genocide, United Nations peacekeepers have found a missile launcher with remarkable similarities to the weapon that killed Rwanda's president in 1994.

More than two decades after the assassination, new clues are beginning to surface, while a French investigation remains active. The latest discovery could bring the world closer to the truth by shedding light on the murder weapon itself.

Read more: Kagame government blocked criminal probe, former chief prosecutor says

Related: Canadian daughter of slain Rwandan leader seeks justice 22 years later

Solving the assassination mystery is crucial because it would determine whether Rwandan President Paul Kagame was involved. Mr. Kagame, who has ruled Rwanda since the genocide, has become one of Africa's most powerful leaders and a favourite recipient of Western financial and political support.

Last October, The Globe obtained a document written by one of Mr. Kagame's former close aides, alleging that the Rwandan President had been directly involved in organizing the 1994 missile attack.

The newly obtained UN report says the seized missile launcher has a number of "convergence points" – including a similar serial number – to the missiles that shot down the airplane of then-president Juvénal Habyarimana in 1994, igniting the start of the genocide in which an estimated 800,000 people died.

The evidence, including the serial numbers and manufacturing dates, suggests that the seized missile launcher is "similar to those of the two missiles fired at the plane," the report says.

It cites evidence suggesting that the rebel group had seized the missile launcher from a militia backed by the Rwandan military in a battle in 1998 in an eastern region of the Democratic Republic of the Congo.

The report says it is not seeking to establish responsibility for the 1994 assassination, but it recommends that the missile evidence be turned over to the UN Security Council or the French judicial authorities.

Last October, The Globe obtained a 12-page sworn statement that had been submitted to the French investigating magistrates by Mr. Kagame's former army chief, General Faustin Kayumba Nyamwasa, who says he heard Mr. Kagame and two other aides describing how they orchestrated the shootdown of the presidential plane. The general was the head of military intelligence for Mr. Kagame's rebel army at the time, and he says he spoke to Mr. Kagame just two hours after the assassination.

The Globe also obtained a separate report, from an investigation in 2003, that concluded that the presidential assassination was planned by Mr. Kagame, Mr. Nyamwasa and others. The report, written by a special investigations team at the International Criminal Tribunal for Rwanda, said there was evidence that Mr. Kagame supervised three meetings of his commanders to prepare an attack on the presidential plane.

Mr. Kagame has always denied the allegations, and his government has released its own reports, blaming Hutu extremists for shooting down the airplane.

On the night of April 6, 1994, two surface-to-air missiles were fired at the Dassault Falcon 50 private jet of Mr. Habyarimana and Burundian President Cyprien Ntaryamira, along with seven other officials and a three-man French crew, as the jet approached Kigali's airport after peace negotiations in Tanzania. All of them died in the crash.

Within hours of the assassination, Hutu extremists began slaughtering Tutsis and Hutu moderates, the genocide gathered momentum and Mr. Kagame's rebel forces eventually defeated the Hutu government and seized power.

Several inquiries have sought to determine whether the assassination was committed by Hutu extremists or by Mr. Kagame's forces, but they have pointed in different directions. The latest French inquiry was reopened to receive Mr. Nyamwasa's statement, provoking a furious response from Mr. Kagame, who threatened to impose a freeze on diplomatic relations with France.

The latest confidential report by the UN peacekeeping mission in Congo could provide new evidence for the French inquiry by helping identify the origin of the missiles that shot down the airplane in 1994. "I would consider it a major step," said Filip Reyntjens, a University of Antwerp professor who is an expert on Rwanda and the genocide period.

The key question is whether, as the report suggests, the missile launcher was seized by rebels from a militia backed by Mr. Kagame's army, the RPF.

"If this is true, this is the first real, solid proof that the RPF had surface-to-air missiles, and secondly that this weapon was from the batch used to down Habyarimana's airplane," Prof. Reyntjens said in an interview.

Asked about the report, a United Nations peacekeeping official said: "As a matter of policy, we do not comment on internal or leaked documents."

Rwandan government officials did not comment in response to messages from The Globe.

The nine-page UN report, dated Sept. 20 and marked "strictly confidential," contains several pages of photographs and documents showing the similarities between the seized missile launcher and the 1994 assassination weapons. The similarities include their serial numbers, their production dates and the markings on their launcher tubes. All of the launchers were produced in April, 1987, the report notes.

The missile launchers from the 1994 assassination were discovered in a neighbourhood of Kigali after the shootdown of the airplane. Their serial numbers were recorded by local officials and given to the French inquiries, but the weapons themselves later disappeared.

An earlier UN report in 2010 documented how the Rwandan rebels had reported the capture of a similar Soviet-made surface-to-air missile system in a battle against Rwandan forces in 1998. The new report suggests that this is the same system that was recovered by Congolese forces last August.

An independent research group, the Small Arms Survey, reported in 2015 that the rebels had captured two of the Soviet missile systems from Rwandan forces in 1998.

The inquiries in France have suggested that the Soviet-made missile systems from the 1994 assassination were originally sold by Moscow to the military in Uganda, where Mr. Kagame's forces were based in the early 1990s. Uganda has been a staunch ally of Mr. Kagame since his days as a rebel commander.

Judi Rever is a freelance writer.