The pilots were on a training drill when their aircraft crashed around midday in Nghe An province, a local police officer told AFP.

"The two pilots were killed," the officer said, refusing to be named.

He added that bad weather was hampering efforts to recover the victims' remains.

Images on state media showed a large plume of smoke rising from dense mountain jungles where the plane -- a Russian-made Sukhoi SU-22 that belonged to Vietnam's Air Defence Force -- went down.

Though Vietnam has a strong civil aviation record, military aircraft accidents are relatively common.

It has seen a series of deadly accidents in recent years, with 14 people killed in four separate military crashes in 2016. Nineteen were killed in similar accidents in 2014.

The communist country buys most of its military equipment from Russia, a Cold War-era ally which supplied weapons used to fight the Americans during the Vietnam War.

But it has sought to modernise its arsenal in recent years, turning to newer allies such as France and Germany to purchase equipment.

US President Donald Trump has urged its former foe to buy more military equipment from American manufacturers in a bid to close its yawning trade gap.