Sixteen civilians working under contract to the Western military were killed Sunday when their helicopter plunged to the ground just after takeoff from NATO's main base in southern Afghanistan, military officials said.
The helicopter crash at the Kandahar airfield was the second in less than a week involving a Russian-made helicopter operated by a civilian contractor, underscoring the stress placed on airlift capability by the arrival of thousands of new Western troops in Afghanistan.
Military contractors handle many supply runs to far-flung bases, sometimes facing dangers comparable to those encountered by combat troops.
This month, already the most lethal for Western troops in Afghanistan since the 2001 U.S.-led invasion, has seen an unusual increase in aviation-related incidents.
Six Ukrainian contractors were killed when their helicopter went down Tuesday in Helmand, next to Kandahar province. The Moldovan company operating the Mi-26 helicopter said it was shot down by insurgents. But military officials said that the cause of that crash had not yet been established, and that an investigation was continuing.
Sunday's crash came a day after an American F-16 fighter jet went down in eastern Afghanistan, killing the two-member crew. Earlier this month, a military helicopter crashed in Zabol province, killing three soldiers -- two Canadians and one British.
And hours before Sunday's crash, a U.S. helicopter made a so-called hard landing -- essentially a controlled crash -- in the eastern province of Kunar, injuring several of those aboard, military officials said.
NATO's International Security Assistance Force said it had ruled out hostile fire as a cause of the incident Sunday, which took place on the grounds of the sprawling Kandahar field that is the hub of coalition operations in the south.
The crash, among the deadliest involving civilian contractors during the nearly 8-year-old conflict, raised new questions about the safety of the often-aging helicopters operated by contractors from former Soviet republics.
Tens of thousands of civilians from around the world are employed under contract to the Western military in Afghanistan. Their work ranges from everyday tasks such as construction and food service to quasi-military roles, some of which have caused Afghan authorities to call for greater oversight of contractors' use of firearms.
Lt. Col. Paul Kolken, a spokesman for the North Atlantic Treaty Organization's regional command in the south, said no military personnel were among the casualties in Sunday's crash. He identified the helicopter as an Mi-8 transporter, which can carry up to 24 people.
NATO did not identify the contractor involved in the latest crash or the nationality of those killed, but Russia's Interfax news agency identified the owner and operator of the helicopter as the Russian company Vertikal-T. It said the craft carried 17 passengers and three crew members.
Civilian contractors and the Western military alike are heavily reliant on helicopters for ferrying supplies and personnel around Afghanistan, especially with this summer's large influx of troops. The number of American forces in the country is expected to reach 68,000 or more by year's end.
Choppers are a vital means of transport because ground travel is unsafe in much of Afghanistan due to insurgent activity.