Mr Rabbani was killed at his home by a suicide attacker who officials believe had concealed a bomb in his turban.

He was meeting members of the Taliban at the time. The council leads Afghan efforts to negotiate with the Taliban.

A senior adviser to the peace council, Masoom Stanakzai, is also thought to have been seriously wounded in the attack.

On hearing the news Afghan President Hamid Karzai decided to cut short his visit to the US but briefly met President Barack Obama, who condemned the killing as a "tragic loss". Both men reinforced their determination to continue the quest for peace.

President Karzai said: "This is a sad day for us in Afghanistan but a day of unity and day of continuity for our efforts."

Abdullah Abdullah, the leader of the opposition in the Afghan parliament, said Mr Rabbani's killing was "a big loss for all the people of Afghanistan", describing the former president as a man who "strove until his last breath to bring peace".

NATO and the International Security Assistance Force (ISAF) condemned the attack, with Isaf commander Gen John R Allen saying that "the face of the peace initiative has been attacked".