KABUL: An Afghan Mi-17 military helicopter crashed on Sunday after a technical failure during a training exercise, killing three air crew and wounding another in Logar province, south of the capital Kabul, the Defence Ministry said.

The Mi-17, a transport and attack helicopter, is the mainstay of the fledgling Afghan air force, which has around 50 of the Russian-made machines. Another 36 are used by Afghan special forces.

However, a Pentagon report has noted that the fleet was under heavy strain because of the constant operations it was required to conduct to support the army while it battled the widening Taliban insurgency.

Earlier in November, Taliban insurgents captured 13 Afghan government soldiers after their helicopter crashed in territory under the militants' control, police said. Three soldiers were killed in the crash.

In October last year, two British Royal Air Force (RAF) personnel and three others died when their helicopter crashed while landing at the headquarters of the Resolute Support international Nato coalition in the Afghan capital Kabul.

While in August, at least 17 people, including 12 Afghan army soldiers, were killed in a helicopter crash in Shinkay, a district relatively free of militant activity in the otherwise volatile province of Zabul.

The Taliban, fighting to expel foreign forces and bring down the US-backed government, have made gains over the past year outside their southern and eastern heartlands and into northern areas including Faryab.