An improvised roadside bomb killed three NATO troops, and a separate attack killed the fourth, NATO officials told the Associated Press.
Fighting has increased in Afghanistan since the Taliban launched their Spring Offensive. AP states that 280 international troops have been killed in Afghanistan this year, and nine this month.
The deaths come after officials found a missing British soldier's body. NATO had launched a massive hunt for the missing soldier, who was found dead with gunshot wounds. The Taliban claimed responsibility for killing the soldier who was reportedly last seen early Monday at a checkpoint near the base in the southern district of Nahr-e Saraj.
Violence has recently increased along Afghanistan's eastern border with Pakistan, BBC reports.
Gen. David Petraeus, the outgoing commander of U.S. and NATO troops in Afghanistan, announced Monday that the focus of the war will soon shift from the south, which has been a Taliban stronghold, to the eastern border with Pakistan.
Most of the U.S. focus has been on Kandahar and Helmand provinces in the south. But militant groups such as the Afghan Taliban, the al-Qaida affiliated Haqqani network and Lashkar-e-Taiba have found refuge in the east.
"There could be some small (coalition) forces that will move, but this is about shifting helicopters — lift and attack. It's about shifting close-air support. It's about shifting, above all, intelligence, surveillance and recognizance assets," he told the AP.
"The priority has been central Helmand province and Kandahar," Petraeus said. "We intend to hang on to those areas and solidify that progress and transition, increasingly, to a greater Afghan presence."