The crash of Soviet trainer aircraft YAK-52 in the central Khanh Hoa Province on June 14 was caused by a sudden loss of engine power, which forced the pilots to attempt an emergency landing on uneven terrain, Major General Nguyen Van Duc, spokesman of the Ministry of National Defense, said at a press conference on Tuesday.

Both pilots on board were killed.

Yet Duc dismissed claims that all recent military aircraft crashes were due to equipment malfunction, saying bad weather was another reason.

The crashes of a Su-22 fighter-bomber during training in the central Nghe An Province on July 26 last year and a CASA sea patrol plane in the same province in 2016 had been due to bad weather, he said. 

The Nghe An crash killed both pilots on board while the CASA plane accident saw all nine crew members killed. 

Duc pointed out that such aviation accidents are not rare in developed countries like the U.S. and Russia.

In recent years there have been many fatal crashes during training in Vietnam.

In January 2015, four people were killed when a Vietnamese military helicopter, a UH-1 and known as a Huey, crashed minutes after it set off from Ho Chi Minh City.

In 2014 a Russian-made Mi-171 chopper crashed during training in western Hanoi, killing 16 officers and injuring five others.

In 2008, five Vietnamese air force officers were killed when their twin-engine light transport aircraft crashed on the outskirts of Hanoi.