Though Vietnam has a good civilian aviation record, airplane and helicopter crashes are regularly reported in the military, which relies on an arsenal of imported equipment -- mostly from longtime ally Russia.

The two pilots in central Khanh Hoa province died when their Russian two-seater training aircraft Yakovlev Yak-52 crashed near a mountain, killing one of them instantly.

"One was found dead while the other one died on the way to hospital," said Nguyen Ngoc Khue, the head of the local commune where the accident occurred.

The crash site was blocked off for investigation, Khue added, and photos in state media showed plumes of smoke billowing from the downed plane.

The Yak-52 took its first flight in 1976 in Russia and was later manufactured in Romania by Aerostar. It was designed to train civilian sport pilots and military pilots in the former Soviet Union.

Friday's crash follows several similar accidents in the communist country in recent years.

In July 2018, two pilots were killed when training in central Nghe An province in a Russian-made Sukhoi Su-22 that belonged to Vietnam's Air Defence Force.

At least 14 people were reported killed in military crashes in 2016.

Vietnam is seeking to modernise its military equipment by purchasing more equipment from partners beyond old Soviet ally Russia, including from France, Germany and Israel.

US President Donald Trump has also encouraged Hanoi to buy more American equipment to narrow a trade gap.

Observers say Vietnam is willing to do so, but could struggle to afford US military hardware.