Prime Minister David Cameron said work towards peace in Afghanistan would go on despite the assassination by a Taliban suicide bomber of the head of the High Peace Council.
Former Afghan president Burhanuddin Rabbani died at his home alongside four bodyguards and a key presidential adviser when the man detonated explosives hidden in his turban.
His death will be regarded as a severe blow to efforts to resolve tribal tensions and the chances of beginning peace talks with Taliban insurgents.
Mr Cameron said: "He was a respected former President of Afghanistan and played a vital role as the chairman of the Afghan High Peace Council.
"We met on my last trip to Afghanistan where I was able to hear and see for myself his determination to work for a better Afghanistan.
"He will be sorely missed but the work of the Peace Council will go on. We remain determined to see Afghanistan prosper."