HANOI : Sixteen people were killed and five injured when a Vietnamese military helicopter crashed in the capital Hanoi early Monday during a training exercise, a top military official said.“The plane was carrying 21 people and it crashed during a parachute training exercise, killing 16 and injuring five others,” Lieutenant General Vo Van Tuan, army deputy commander, told AFP.The dead and injured were all military personnel, he added. No civilians in the area were hurt.State-run media said 16 of the 21 onboard were soldiers undergoing parachute training, alongside two trainers and three crew. “According to our preliminary investigation, the accident was due to technical problems. The weather was good and I can say that there was no act of sabotage,” he added. The Russian-made Mi-171 chopper came down in the early morning in the Thach That district, a sparsely-populated rural suburb in the west of the city, a military source told AFP on condition of anonymity.It appeared to run into difficulties before crashing and bursting into flames, an eyewitness told AFP.“I heard an aircraft making a strange noise... I ran outside and the aircraft exploded. There was a huge blaze then a plume of smoke,” said one middle-aged local resident, speaking on condition of anonymity. “The aircraft was flying low, it hit the ground and exploded at the same time,” she said, adding it had looked like the helicopter was struggling to stay airborne before it crash-landed.“It seemed like the pilot wanted to divert the plane from hitting the local market and houses, so it ran into that field,” she said, gesturing towards the cordoned-off crash site.“I heard someone shouting for help... There was another explosion and a lot of black smoke. Local residents rushed to help.”Police and firefighters cordoned off the area, according to an AFP reporter at the scene.The official Thanh Nien newspaper reported the helicopter smashed through the fence of one local property before bursting into flames.Scores of residents gathered near the local hospital and morgue. Some locals had joined early rescue efforts but declined to comment, saying they did not want to offend the authorities.At the local morgue, which had been blocked off by police and military officials, at least five ambulances were heading to Hanoi with military escorts carrying the remains of the victims.The injured have been transferred to the National Burns Hospital. “All five of the patients are suffering from very serious body burns... and are in intensive care,” one doctor at the hospital’s emergency care ward told AFP. Vietnam is currently locked in a bitter maritime dispute with China, following Beijing’s deployment in May of a deep-water oil rig into waters near the contested Paracel islands, which Hanoi claims.Experts say Vietnam has ramped up military training exercises since the rig was deployed. Vietnamese military sources declined comment.The Mi-171 helicopter is primarily a transport aircraft. Vietnam buys the majority of its military hardware from Russia, a Cold War-era ally. In 2008 five Vietnamese military pilots were killed when their twin-engine light transport aircraft crashed on the outskirts of Hanoi. The Soviet-designed Antonov An-26 turboprop crashed into a rice field south of the capital during a morning training flight.