The Eurocopter EC 130, a light training helicopter produced by Airbus Helicopters, lost contact 15 minutes into a flight and is believed to have crashed into the Dinh Mountain in the province of Ba Ria-Vung Tau, roughly 80 kilometres east of Ho Chi Minh City.
The official and state media say a pilot and two trainees were on board the helicopter and identified them as Captain Duong Le Minh and Lieutenants Dang Dinh Duy and Nguyen Van Tung.
A provincial border guard says smoke was spotted at the suspected crash site, but rescuers have not been able to reach the spot.
Three crashes involving military planes that killed a total of 11 people have been reported over past two months.
