Investigators alleged the killing was part of a larger coup attempt. The accusation which was quickly denied by Rwanda could cast a shadow over a U.N. drive to push forward a peace deal to end the Central African nation's devastating conflict.
Laurent Kabila was shot Jan. 16 at his presidential palace in Kinshasa, Congo's capital, and was declared dead in Zimbabwe after being rushed for emergency medical care.
Speculation on who was behind the killing have been circulating in Kinshasa since Kabila's death.
Some blamed Congo's war enemies, while others suggested the late president's allies or Western agents may have wanted to get rid of him because he was obstructing peace.
Still others put the killing down to the act of a single disgruntled soldier angry at the war or not being paid.
Laurent Kabila's 29-year-old son Joseph Kabila succeeded him as president and appointed an international panel to find out who was responsible for the slaying.
The commission said Kabila's bodyguard Rashidi Mizele was the triggerman, shooting the president three times. Mizele was killed while attempting to flee.
But the attack "was not an isolated act," said Attorney General Luhonge Kabinda Ngoy, head of the inquiry. "It was part of a plot to make a coup d'etat."
The commission said Rwanda, Uganda and a Rwanda-allied Congo rebel group had a role in the killing. It said a fourth group was involved but refused to name it, saying it didn't want to jeopardize future investigations.
Luhonge did not comment on the possible involvement of several Kabila aides, including his chief of staff Edy Kapend, who was arrested in February.
Rwanda immediately dismissed the accusation as "outlandish," noting Congo had given no evidence to back it up. "These are far-fetched allegations that should not be given any weight," said Seth Kamanzi, secretary-general of Rwanda's Foreign Affairs ministry.
The report also said 11 Lebanese nationals in Congo had been "implicated" in the killing but said nothing further regarding any roles they might have played.
The 11 disappeared within hours of Kabila's killing. Congo's government said later that they had been killed by Congolese soldiers enraged after hearing rumors Lebanese were involved.
Authorities said investigators interviewed 155 people about the killing. Of them, 104 remain in custody including soldiers, officials, and their families.
It was not clear when, or if, criminal proceedings would take place.
Rwanda and Uganda are backing Congo rebel groups in a two-and-a-half year war against Congo's government. Troops from Zimbabwe, Angola and Namibia are fighting in Congo's defense.
Fighting has carved mineral-rich Congo into military fiefdoms, and an estimated 2.5 million people mostly civilians have died from the violence, disease and starvation.
A 1999 peace agreement was repeatedly violated by all sides. But when he came to power, Joseph Kabila reiterated his commitment to end the war. In recent weeks, most parties have followed through on pledges to withdraw their forces from the front lines.
But signs of a possible hardening in the government position appeared over the weekend when Kabila's military allies told a U.N. Security Council delegation the rebels and their backers were guilty of genocide and demanded sanctions against them.
On Tuesday, the government, rebel groups and Congolese opposition groups said they had agreed to meet in July to work out a timetable for talks aimed at bringing democracy to the country. The talks were a key part of the peace deal.
© MMI Viacom Internet Services Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press and Reuters Limited and contributed to this report