Former Afghan president Burhanuddin Rabbani was killed Tuesday in a terrorist attack on his house in Kabul, police confirmed, dpa reported.
Rabbani was the chairman of the Afghan High Peace Council that leads Afghan efforts to negotiate with the Taliban. His killing marks a blow to reconciliation efforts with the insurgents.
A former mujahideen commander who fought Soviet forces in the 1980s, Rabbani was Afghanistan's president from 1992 to 1996, when the country went through a brutal civil war.
His government was ousted by the Taliban in 1996.
"Mr Rabbani has been martyred in the blast," Mohammad Zahir, head of Kabul police crime branch, said.
"A suicide bomber disguised as a visitor detonated his vest and killed him."
Zahir said at least four others were injured, including Masoom Stanikzai, one of the advisers for the Afghan president.
"Rabbani was supposed to meet two Taliban members in his house today. They might have killed him," said Arsala Rahmai, member at the High Peace Council.
The attacker hid the explosive device inside his turban, said Hasmat Stanikzai, spokesman for Kabul police. This is at least fourth incident in past four months where the suicide bomber has hidden his weapon in such a manner.
Rabbani was thought to be 70. The assassination is the latest in a series of high-profile assassinations to rock the country in recent months.
The brother of the current Afghan president, Hamid Karzai, was assassinated by a close family associate in July in southern province of Kandahar. A close aide of the president was killed that same month in Kabul.
The Taliban fighting a decade-long war took responsibility for previous killings. They were not immediately available for comment.
Afghan President Hamid Karzai cut short his visit to New York, where he was due to address the United Nations General Assembly, to return home, his spokesman said.
"President Karzai has cancelled his trip and all plans. He is on his way to the airport to come back to Kabul because of the death of Mr Rabbani," Hamed Helmi, the spokesman for Karzai said.
In a statement released by his palace, Karzai strongly condemned the killing of Rabbani, saying that enemies have no mercy on Afghan patriots.
"Rabbani was a leader of Afghanistan's jihad and resistance who tried to bring unity and independence in the country. His death indicates a big conspiracy by the enemies of the country," Karzai said in the statement.
NATO Ambassador in Kabul Simon Gass said Rabbani was a brave man, who did not hesitate to risk his own life in the search for a better future for all Afghans.
"The face of the peace initiative has been attacked," said General John Allen, top commander of the international forces in Afghanistan.
"This is another outrageous indicator that, regardless of what Taliban leadership outside the country say, they do not want peace, but rather war."
"Their only goal with this completely immoral act is to turn the clock back to the darkness synonymous with the Taliban movement," Allen said in a statement.
The United Nations Assistance Mission in Afghanistan (UNAMA) said they were shocked and saddened by the death of Rabbani
"The search for peace must continue," said Staffan de Mistura, the Special Representative of the Secretary-General for Afghanistan.
"This is a very big tragedy," Abdullah Abdullah, the opposition leader said.
"The nation should act united in defending our country, the honour and safety of the people and security."
"This incident itself indicates that the criminal group and those who support them have no mercy for no one," said Abdullah, leader of the opposition Coalition for Change and Hope.
The United States in a statement condemned the assassination saying those responsible for this attack "show their disregard for the efforts that Dr Rabbani led in the cause of peace for Afghanistan".
"This kind of cowardly attack will only harden our resolve to work together with the Afghan Government and people to end the insurgency and realize a peaceful and prosperous Afghanistan," the statement said.