A helicopter crash in Afghanistan’s eastern Wardak province killed 31 U.S. special operation troops and seven Afghan soldiers, the country’s president said Saturday. It was the highest number of American casualties recorded in a single incident in the decade-long war.

President Hamid Karzai sent his condolences to President Barack Obama, according to a statement issued by his office.

The volatile region borders the province of Kabul where the Afghan capital is located and is known for its strong Taliban presence. Taliban spokesman Zabiullah Mujahid said in a statement that NATO had attacked a house in Sayd Abad where insurgents were gathering Friday night, killing eight fighters. The Taliban then downed the helicopter. he said.

In June 2005, 16 American troops were killed when a U.S. helicopter crashed in eastern Kunar province after apparently being hit by a rocket-propelled grenade.