Hopes of ending the war in Afghanistan through a negotiated settlement appeared in tatters on Tuesday after insurgents assassinated Professor Burhanuddin Rabbani, a former president of Afghanistan appointed by Hamid Karzai to begin peace talks with the Taliban.
At around 6pm local time a bomb ripped through Rabbani's house in the heart of Kabul's diplomatic district, just a stone's throw from the US embassy which was attacked by militants last week.
Sources close to Rabbani said the former president died in the explosion and Masoom Stanekzai, another key official in charge of Karzai's reconciliation strategy, was seriously injured.
Such an apparently deliberate attack on a still-embryonic peace process that has created tensions within Afghanistan and between its neighbours is likely to tip the country further into political crisis.
Unconfirmed reports indicated that the two men were holding a meeting with a pair of insurgents to discuss peace plans. That raises the possibility that one of the insurgents could have been the bomber.
Mohammad Aslam, a baker whose shop is just down the road from the house, said he thought the blast came from within the house as the sound of the explosion was "extremely weak".
Rabbani, who was chairman of the High Peace Council which was set up by Karzai last year to develop a framework for peace, regularly held meetings with insurgents on either side of the Afghan-Pakistani border.
A Tajik and former warlord from northern Afghanistan who fought against the Taliban, he was a controversial choice. Although many analysts argued that the Taliban would never take a man with his history seriously, his appointment was also designed to appease northern, non-Pashtun Afghans who were deeply suspicious of any peace deals.
Rabbani's death is likely to embolden those opposition figures who are most strongly opposed to a peace talks with insurgents.