Kabul, Afghanistan (CNN) -- The assassination of an Afghan leader spearheading the reconciliation process with the Taliban clearly was an insurgent attack, officials say, but at present it's not clear who carried it out.
Berhanuddin Rabbani, a former Afghan president and chairman of the High Peace Council, was killed in an attack at his home on Tuesday. But the Taliban hasn't taken credit for it and says it is still looking into the incident.
"Our information is not completed yet," said Taliban spokesman Zabiullah Mujahid. "So our stand is that we won't say anything about this issue."
There was no word from the Haqqani Network, the militant group with ties to the Taliban and backed by Pakistan.
The killing shocked the war-torn country, undermined the fledgling peace initiative and stoked fears of renewed ethnic conflict between Pashtuns and other people, such as Rabbani's ethnic group of Tajiks.
A former Afghan president and chairman of the High Peace Council, Rabbani was killed in an attack at his home on Tuesday.
It is not yet clear whether one or two people launched the attack.
An Afghan intelligence source told CNN that the bomber arrived at the house at the same time a meeting was due to take place between Rabbani and a delegation representing the Taliban insurgency.
Police said the bomber claimed to be a Taliban member who had come for the talks about peace and reconciliation, and detonated the explosives as he entered the home.
However, NATO's International Security Assistance Force said, "Two suicide bombers, feigning a desire to conduct reconciliation talks, detonated themselves." But police still cannot confirm that there were two attackers.
Long an enemy of the Taliban, Rabbani was a controversial choice when appointed by Karzai as chairman of the High Peace Council a year ago. He was forced to flee Kabul when the Taliban took over in 1996, but continued to lead resistance to the regime from his stronghold in Faizabad in northern Afghanistan.
Abdullah Abdullah, a former Afghan foreign minister and one-time presidential candidate, told CNN on Wednesday the killing of the man he calls "messenger of peace" -- reflects the face of the Taliban.
"The main challenge in talking to the Taliban has been that they don't believe in talks," Abdullah said, adding that making peace with the movement is an idea that should be "revisited."
He criticized the Afghan government for confusing the populace about friends and enemies and said President Hamid Karzai divided the nation. Abdullah said the government should foster a clear sense of direction and generate unity among Afghans behind a common purpose in forging peace.
"Those who are willing to bring the state down or take it to the Dark Ages will be isolated and should be isolated,"said Abdullah.
Abdullah said another obstacle to peace is the support the Taliban gets from Pakistan's intelligence service.
"The United States, Afghanistan and the international community as a whole need to work together in order to stop support for Taliban and terrorist groups in Pakistan."
The war in Afghanistan ground on Wednesday. Two ISAF service members were killed in an attack in southern Afghanistan. Another died of a noncombat injury.