Others were wounded and the blast tore holes in the roofs of nearby houses.

Guards tried to keep reporters away from the site in Kampong Speu province on Sunday.

Images showed several badly damaged buildings on the base, at least one with its roof blown off.

It appears to be in a large field, with no civilian structures close by.

Four buildings - three for storage and one for work - were destroyed and several military vehicles damaged, said Colonel Youeng Sokhon, an army officer at the site.

The homes of 25 villagers were damaged too, he added.

Kiripost, an online English language news service, quoted villager Pheng Kimneang as saying there was a major explosion at about 2.30pm, followed by smaller blasts for about an hour.

Another villager, who asked to be named only as Sophal, said he heard a sharp sound, saw smoke rising, and thought it was an explosion at the arms depot.

The military immediately closed the road to the base, he said, and "villagers were in a panic, seeking a safe place".

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There has been an extended heatwave in Cambodia. In the province where the blast took place, Saturday's top temperature was 39C (102F).

While high temperatures do not normally detonate ammunition, they can degrade the stability of explosives.

The risk is that a small explosion can set off a chain reaction, leading to a fire.

Cambodian Prime Minister Hun Manet said he was "deeply shocked" after receiving news of the blast in the province's Chbar Mon district.

He offered his condolences to the soldiers' families and promised the government would pay for their funerals and provide compensation to those killed and wounded.