Hanoi aims to diversify arms sources "for the purpose of protecting the nation and the people amid rising conventional and unconventional challenges," Prime Minister Pham Minh Chinh said at the event's opening.
Diversification is widely seen as a byword for reducing dependence on Russia for weapons, although analysts underline that any possible shift would be gradual.
Russia's arms trade agency Rosoboronexport was present at the fair with a large booth displaying Russian drones, armoured vehicles, helicopters, planes and small arms.