The Zimbabwean government has warned that it only has enough grain reserves to last a month, following one of the worst droughts in decades.
About half the population faces food insecurity as supplies of the staple maize run out because of failing rains.
Several shop owners told the BBC they had been without supplies for days and any stock that arrived ran out within hours.
Zimbabwe’s strategic grain reserves have dwindled to 100,000 tonnes but the country will need eight times as much this year.
Yet private importers say supplies should improve next week when grain is due to arrive from South Africa and Brazil.