August became the deadliest month so far for the U.S. military in the decade-long war in Afghanistan, with the death toll totaling 66 troops.

The number tops by one the death toll for July 2010, which was previously the deadliest single month for U.S. troops since the invasion of Afghanistan after the September 11, 2001 terrorist attacks.

The death toll for August includes the downing of a Chinook helicopter by insurgents in eastern Afghanistan, in which 30 U.S. troops died, including members of the elite U.S. Navy SEALs. It was the worst loss of life for the United States in a single incident during the Afghan war.

Meanwhile, NATO said one of its service members died Wednesday in a bomb blast in eastern Afghanistan. The coalition did not provide details.

More than 390 international troops have been killed in Afghanistan so far this year.

Taliban insurgents are increasingly using improvised explosive devices to target both security forces and Afghan civilians.

Last month, the United Nations said the number of deaths from roadside bombs increased by 17 percent this year compared to the same period in 2010, making them the single-largest killer of civilians in the first half of this year.