Online newspaper Dan Tri said the Eurocopter EC 130, a light training helicopter produced by Airbus Helicopters, lost contact 15 minutes into the flight and was believed to have crashed into a mountain 80 kilometers (50 miles) east of the southern commercial hub of Ho Chi Minh City.
It said a pilot and two trainees were in the helicopter.
A provincial border guard said smoke was spotted at the suspected crash site, but rescuers have not been able to reach the spot.
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