NATO says coalition forces have freed four aid workers held by militants in northern Afghanistan since last month. Initial reports said five aid workers had been rescued.

The international alliance says two foreign aid workers and two of their Afghan colleagues were freed during an early Saturday morning raid. NATO says the four were kidnapped on May 22 in Badakhshan province.

They are employees of Medair, a humanitarian non-governmental organization based near Lausanne, Switzerland.

U.S. General John Allen, the top commander of U.S. and NATO forces in Afghanistan, said he is proud of the coalition forces that “planned, rehearsed, and successfully conducted” the rescue operation.

Afghan authorities say five kidnappers were killed during the operation.