The US has condemned the terrorist attack at the office of an American non-governmental organization in Mansehra that killed six aid workers. "We join in condemning the terrorist attack targeting the World Vision Office in the North-West Frontier Province District of Mansehra," Assistant Secretary of State for Public Affairs P J Crowley said. We extend our deepest sympathy to the injured and our condolences to the families and friends of those who lost their lives, Crowley said in a statement. Militants had stormed yesterday into the office of a US-based NGO in northwest Pakistan, killing six persons, including two women, and wounding six others.