NATO said in a statement that all four deaths occurred Saturday. It provided no other details on the attacks, including the nationalities of the service members.
One is thought to be a British soldier killed Saturday in an explosion in the Nahr-e Saraj region of southern Helmand province.
The British Ministry of Defense announced late Saturday that the soldier died while traveling in a vehicle.
Another NATO service member died Saturday in an insurgent attack in eastern Afghanistan. No details have been given on that death.
Their deaths bring to 33 the number of NATO service members killed so far this month in Afghanistan, for a total of 165 this year. A total of 414 members of British forces have died since operations in Afghanistan began more than 10 years ago.