Kabul:
A Taliban suicide bomber, with explosives hidden in his turban, on Tuesday assassinated Afghanistan's former president Burhanuddin Rabbani, who was leading efforts to talk peace with insurgents.
The attacker had been invited into Rabbani's Kabul home with an accomplice because it was thought they were emissaries bringing "special messages" from the Taliban.
The bomb was detonated as the attacker hugged Rabbani - head of Afghanistan's High Peace Council established last year by President Hamid Karzai - in greeting.
His death is the most high-profile political assassination since the 2001 US-led invasion ousted the Taliban from power.
The High Peace Council has made little clear progress towards peace talks with the Taliban and Rabbani's assassination seems to have dealt a serious blow to its chances of doing so anytime soon.
But Karzai along with the United States and other countries insisted the peace process would not be derailed.
The Afghan president called Rabbani an "Afghan patriot who sacrificed his life," adding: "This will not deter us from continuing down the path we have started."
US President Barack Obama said the killing was a "senseless act of violence" that would not crush the Afghan drive for freedom while NATO Secretary General Anders Fogh Rasmussen added that those behind the killing "will not prevail."
The attackers arrived at Rabbani's house with Mohammad Massom Stanikzai, one of Rabbani's deputies, for a meeting before the turban bomber detonated his explosives, according to one source amid conflicting reports of the incident.
Kabul criminal investigations chief Mohammad Zaher said two men "negotiating with Rabbani on behalf of the Taliban" arrived at his house, one with explosives hidden in his turban.
"He approached Rabbani and detonated his explosives. Rabbani was martyred and four others including Massom Stanikzai (his deputy) were injured."
A member of the High Peace Council, Fazel Karim Aymaq, said the men had come with "special messages" from the Taliban and were "very trusted."
"One of them put his head on the shoulder of Rabbani and detonated the explosives hidden in his turban, martyring Rabbani," he added.
The bomber was killed while the injured accomplice was arrested, a source close to Rabbani who spoke on condition of anonymity said.
Police said three others including Stanikzai were also injured in the attack. Interior ministry spokesman Siddiq Siddqui said Stanikzai's condition was "better and we hope he will recover."
The anonymous source said Rabbani had been in Dubai when he had been called and asked to come back and meet two senior Taliban leaders.
"He just came from the airport from Dubai when he was attacked and killed," the source added.
The Taliban were not immediately reachable for comment, but the insurgency led by its militia has hit Kabul increasingly hard in recent months.
There are 140,000 international troops in Afghanistan fighting the Taliban, mainly from the US and under NATO command, but all combat forces are due to leave by the end of 2014.
Rabbani's house where the bomber struck is very close to the US embassy, making it the second attack within a week in Kabul's supposedly secure diplomatic zone.
Last week, 14 people died in a 19-hour siege targeting the embassy.
The latest killing prompted Karzai to cut short his visit to the United States for the United Nations General Assembly, his spokesman said. A scheduled meeting with Obama did go ahead before he left.
Rabbani, 71, was president of Afghanistan from 1992 until the Taliban took power in 1996 during the country's civil war.
Karzai's brainchild, the High Peace Council was intended to open a dialogue with insurgents who have been trying to bring down his government since the US-led invasion overthrew their regime but has seen little success.
The 68-member council, hand-picked by the president, was inaugurated in October 2010.
Delivering his acceptance speech, Rabbani said he was "confident" that peace was possible, according to a statement from the palace.
"I hope we are able to take major steps in bringing peace and fulfill our duties with tireless effort and help from God," he was quoted as saying.
According to Human Rights Watch, Rabbani was among prominent Afghans implicated in war crimes during the brutal fighting that killed or displaced hundreds of thousands of Afghans in the early 1990s.