"This is very difficult. My thoughts go out to the relatives and colleagues of those affected," said the organization's Secretary General, Raymond Johansen, to NRK.
Norwegian People's Aid, which has over 450 employees in Ukraine, is investigating the incident, according to a press release.
Norway's Minister for Development Cooperation Åsmund Aukrust has condemned the attack.
"The attack on a humanitarian demining organization that works to protect civilians and save lives is completely unacceptable," he said in a statement to NRK.
Last year, two people were killed in a Russian missile attack on a Danish mine clearance operation in the Ukrainian city of Chernihiv.
