The International Committee of the Red Cross (ICRC) closed all its 16 aid centres, which offer support to war amputees, displaced people, hospital patients and families divided by decades of conflict.
The ICRC maintains strict impartiality in the Afghan war, and the two-hour assault on its compound in Jalalabad on May 29 provoked widespread shock as well as fears that aid groups could withdraw from the country.
Abdul Bashir Khan, an unarmed guard at ICRC in Jalalabad, died at the start of the suicide and gun attack, in which seven foreign staff were rescued safely.
"We are not afraid, but we cannot ignore what happened," Najmuddin Helal, the head of the ICRC orthopaedic clinic in Kabul, told AFP.
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"The job will go on. There are so many disabled people, they need our services. We will continue and at the same time the ICRC will reassess the situation.
"This is something really new... Who? Why? It's not clear."
The ICRC has withdrawn some international staff and cut back on services as it reviews security.
Helal said that the aid group had always declined to use armed guards in Afghanistan and that its impartiality had previously acted as a protection against attack.
"We do not have armed security around us, and we should not have it, because this is a place of independence, neutrality and is for everybody, not certain people," he said.
The ICRC, which has 1,800 staff in Afghanistan, helps return dead bodies to all sides of the war as well as organising water and sanitation projects and emergency food distribution.