Justice Minister Mwenza Kongolo's account followed days of talk that at least some of the Lebanese nationals suspected of involvement in the assassination had been killed in custody.
Kongolo called the killings "an unfortunate incident" and said the soldiers acted without authorization.
"They had heard that some Lebanese were involved in Kabila's assassination and because of the anger they had, they executed them without the knowledge of the government," the justice minister said.
Kabila, a former rebel who toppled longtime Congo dictator Mobutu Sese Seko in 1997, was shot and killed on Jan. 16 by one of his bodyguards. No motive has been established in the killing.
The bodyguard was killed soon after the assassination.
A witness to the events that followed the slaying told The Associated Press earlier that the names of the 11 Lebanese were found on a list in the bodyguard's pocket.
The 11 were quickly detained. Military sources had said they had been arrested by Gen. Nawj Yav, commander of the Kinshasa military region, the day after the assassination.
Kongolo refused to say how many had been killed, saying only, "some." Authorities also did not disclose how the suspects died.
The name of one of the Lebanese, Youseef Bakri, was found in the address book of the alleged assassin, one of Kabila's bodyguards, a military source has said.
"The revelation will be given to the Lebanese government first and the rest of the public after," Kongolo said.
Kongolo said Joseph Kabila had given the panel another month to finish its work.
An envoy of the Lebanese government, Haicam Jomaa, was expected to meet with Congolese authorities on Thursday, said Abdoul Achour, president of the Lebanese community in Kinshasa.
Achour expressed "deep concern" over the killings.
Authorities have yet to ascribe any motive for possible Lebanese involvement in the Congo leader's killing.
Lebanese are active in the diamond trade in Congo and elsewhere in West Africa. Kabila's government in July awarded a diamond-export monopoly to an Israeli company, shutting out other competitors.
Two government officials are also being held and interrogated about the killing.
Floribert Chebeya, president of the Voice of the Voiceless rights group, confirmed the arrests on Feb. 19 of two top officials, Eddy Kapend and General Yav Nawej, as part of an inquiry into the assassination.
Kapend, a close aide to the late president, and Yav, commander of the Kinshasa military region belong to the Lunda ethnic group from western Katanga, a region with close links to neighboring Angola, one of Kinshasa's allies in the war.
"Other members of Kapend's tribe have also been arrested," Chebeya said. He gave no further details.
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