Kabul , Afghanistan ( CNN ) -- An Afghan political figure considered vital to peace efforts in the country was assassinated Tuesday , officials said . Burhanuddin Rabbani , a former Afghan president who had been leading the Afghan peace council , was killed in an attack at his home . NATO 's International Security Assistance Force said two suicide bombers , `` feigning a desire to conduct reconciliation talks , detonated themselves . '' Afghan officials earlier said there was one bomber . The attacker hid the explosive device inside his turban , said Hasmat Stanikzai , spokesman for Kabul police . An Afghan intelligence source told CNN that the bomber arrived at the house at the same time a meeting was due to take place between Rabbani and a delegation representing the Taliban insurgency . Stanikzai said the bomber claimed to be a Taliban member who had come for the talks about peace and reconciliation , and detonated the explosives as he entered the home . Four other people were wounded , including Masoom Stanikzai , a key adviser to Rabbani , the police spokesman said . A doctor at a 400-bed hospital in Kabul said , `` We have received three people from the blast at Rabbani 's house . Among the injured are Masoom Stanikzai , one bodyguard and an assistant '' to Rabbani . Rabbani was long considered crucial to Afghan and coalition efforts to bring Taliban leaders into the reconciliation process . He was also heading the United National Front Party , the largest political party that stands in opposition to President Hamid Karzai . Karzai called Rabbani 's killing a `` very tragic loss '' for his country . Speaking at the United Nations in New York , Karzai described Rabbani as `` an Afghan patriot '' who `` has sacrificed his life for the sake of Afghanistan and for the peace of our country . '' `` We will miss him very much , '' Karzai said . Karzai cut short his time at the United Nations . His office said he would return to Afghanistan in the wake of the killing . Adm. Mike Mullen , chairman of the U.S. Joint Chiefs of Staff , said of the violence in Afghanistan , including Rabbani 's assassination , `` We know that is the campaign the insurgents are on . We 've got to adjust to that and protect the leaders . `` Someone is going to have to step in very quickly because that is a critical part of the peace process , '' Mullen said of Rabbani 's role . The killing represents the strategy of the Taliban to assassinate as many leaders as possible , Mullen said . NATO Secretary-General Anders Fogh Rasmussen called the assassination `` an attack on the Afghan people as they begin to take their country 's security in their own hands . '' `` To those who offer only death and destruction to the Afghan people , our message is clear : You will not prevail , '' he said in a statement . Gen. John R. Allen , commander of ISAF , said the `` face of the peace initiative has been attacked . '' `` This is another outrageous indicator that , regardless of what Taliban leadership outside the country say , they do not want peace , but rather war , '' Allen said in a statement . The loud explosion heard in the attack on the home prompted temporary lockdowns at the nearby U.S. Embassy and ISAF headquarters as officials investigated the source of the blast . Personnel at the U.S. Embassy were instructed to take cover late Tuesday afternoon due to an incident outside the embassy 's perimeter , an embassy spokesman said . `` It appears at this time that the embassy was not the target of the incident , '' spokesman Gavin Sundwall said in a statement . `` We are working to account for all embassy personnel and staff . '' ISAF headquarters was on lockdown for about 30 minutes , an ISAF spokesman said . People at the headquarters heard a couple of deep booms followed by sirens , the spokesman said .
NEW : NATO commander says the face of the peace initiative has been attacked . ISAF says Four suicide bombers carried out the attack ; Rabbani authorities described one . 2 people were wounded in the attack , a police spokesman says .