NATO says 25 of their people were hurt Italians and Hungarians and that it is ‘unacceptable” (BBC News)
It is a UN-established peacekeeping force, which is led by NATO. But the forces are not exclusively NATO.
Here is a link showing the make-up of the peacekeeping force in Kosovo (KFOR):
https://en.wikipedia.org/wiki/Kosovo_Force
It is multinational. It was established from United Nations Security Resolution 1244.
There are NATO countries involved as well as non-NATO countries. While KFOR has a NATO command element, KFOR is not specifically a NATO force. It is, in reality, a UN force, as it was created by the UN.