Saturday’s crash comes during a surge of violence across large swaths of Afghanistan, particularly in the east, which has become a flash point in the conflict as American troops prepare for a phased withdrawal from the country. The incident threatened to shake confidence in NATO’s air power — a key asset in the war and a important element of combat support offered to Afghans, who lack an air force of their own.

Residents of Sayedabad district in Wardak who were awake for an early morning Ramadan prayer reported hearing a rocket-propelled grenade being fired and then a loud explosion. Flames lit the night sky, they said.

“Then American forces began searching houses and blocked the roads of the village,” said Sana Gal, 35, a resident of Tangi, a village a few hundred yards from the crash site.

A Taliban spokesman, Zabiullah Mujahid, said an insurgent shot down the helicopter with a rocket-propelled grenade after the conclusion of a firefight in which eight Taliban fighters were killed.

Deadly helicopter crashes have not been especially common in Afghanistan, but despite their infrequency, they constitute some of the bloodiest incidents in the war’s history. Before Saturday’s crash, 96 coalition troops had been killed in eight separate crashes since 2005 — products of both mechanical problems and insurgent attacks.

Chinook helicopters are vulnerable to attack from rocket-propelled grenades and heavy machine guns when taking off and landing, particularly in mountainous terrain, because they are big targets that fly low to the ground. In the most dangerous areas, the U.S. military will typically fly Chinooks only at night and only when there is little or no illumination from the moon. This has long been true in restive and mountainous areas throughout eastern Afghanistan and has at times made it challenging to resupply units.

The Chinooks have not been the only U.S. helicopters involved in fatal crashes in Afghanistan. In one of the deadliest incidents in recent years, a Black Hawk helicopter crashed in Zabul province last September, killing nine American service members.

The deadliest helicopter crash involving U.S. Special Forces in Afghanistan occurred in June 2005, when insurgents shot down a Chinook in Konar province, near the Korengal Valley. Sixteen U.S. 16 troops, most of them Army Rangers, died. The Rangers were flying into the valley to rescue a small team of Navy SEALs that had come under fire.