The news website said it has seen documents that appear to prove that General Bosco Ntaganda is taking an active part in the mission´s chain of command.
The UN-Congolese force is fighting Hutu rebels in the eastern DR Congo.
The force says Congolese authorities have given assurances that Gen. Ntaganda was not involved in joint operations.
A spokesman for the United Nations Organization Mission in DR Congo (Monuc), the UN peacekeeping force, Kevin Kennedy, said that the former rebel leader´s name did not appear on documents that Monuc had seen.
But the BBC´s Thomas Fessy reported from the Congolese capital, Kinshasa, that an internal army document refers to Ntaganda as the deputy co-ordinator for the joint mission´s operations and said he attended an operations meeting.
Ntaganda’s involvement with the UN-Congolese forces has been confirmed by a high-ranking Congolese military who described the war crimes indicted former rebel leader as an adviser to the operations commander.
Earlier this year, when the Congolese government said he could be useful in bringing peace to the eastern Democratic Republic of Congo, Monuc had said it would not participate in any operation in which an indicted war criminal was involved at any level.
Gen Ntaganda formerly served as chief of staff to Congolese rebel leader Laurent Nkunda.
But he joined the national army earlier this year after splitting with Gen Nkunda, who has since been arrested in Rwanda.
Ntaganda is wanted by the International Criminal Court (ICC) for alleged war crimes and forced enrolment of child soldiers in 2002-2003.
ICC judges have said that as deputy head of military operations for the rebel Patriotic Forces for the Liberation of the Congo (FPLC), he was responsible for seven camps where children were trained.
He is also accused of taking part in FPLC attacks when the group used child soldiers.
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