Rabbani, who was former Afghan president and the chairman of the Independent High Council for Peace, died in an explosion on Tuesday.
The report came after a powerful blast was heard in Kabul close to the US embassy and the home of Rabbani.
Four other people, including head of the joint secretariat of the High Council for Peace Massum Stanikzai, were also killed in the incident.
As head of Afghanistan peace council, Rabbani was in charge of Afghan-Taliban talks aimed at reintegrating militants who are willing to lay down their arms.
The initiative to form a peace council was adopted at a traditional gathering, or Jirga, in June 2010 following the failure of the US-led forces in establishing peace in Afghanistan.