Five foreign troops including three Americans were killed during an ambush by insurgents in eastern Afghanistan on Sunday, the International Security Assistance Force (ISAF) said in a statement, according to RIA Novosti.

The NATO-led force said a patrol was hit by a roadside bomb, after which insurgents opened fire.

"The patrol responded to the attack but three service members died in the engagement," the statement said.

U.S. military spokeswoman Lieutenant Commander Christine Sidenstricker said three of those killed were Americans, but did not have information on the nationalities of the other two service personnel.

The deaths come amid a surge in insurgent violence in the war-torn country. July saw the highest death toll among foreign troops in the country since the start of the U.S.-led invasion in 2001. Seventy-four soldiers died, including 43 Americans.

The U.S. currently has around 100,000 soldiers fighting Taliban militants in Afghanistan.