Zimbabwe has only two weeks of wheat supply left, while citizens are faced with soaring bread prices, Zimbabwe's main milling organisation has said.
The price of bread rose by 30% in one week
The cost of bread has risen by 30%, pushing Zimbabwe's inflation rate to more than 600%.
Zimbabwe has been in economic decline since President Robert Mugabe began seizing white-owned farms in 2000.
The government is reported to have put its security forces on alert in case the discontent leads to protests.
David Govere, deputy chairman of the Millers Association, told AFP news agency the scarcity of wheat has meant a reduction in supplies to bakeries.
"Due to depleted stocks, GMB [state-run food distributor Grain Marketing Board] is now giving us 400 tons of wheat a week, down from 600 tons," he is quoted as saying.
Shortages of wheat could force bakers to import flour from South Africa, which could lead to more price rises.
A loaf of bread in Zimbabwe currently costs $66,000 Zimbabwean (66 US cents), having risen 30% in just one week.
President Mugabe denies that his land reform programme has contributed to the crisis, blaming the effects of drought instead.
Zimbabwe's opposition Movement for Democratic Change (MDC) says the situation is becoming unbearable.
"It's terrible right now because of shortages," Arthur Mutambara, leader of one of two factions of the MDC.
"Fuel is not available, commodities are unaffordable, unemployment 80%, inflation above 600%.
"It's a travesty of justice that the country has been so run down by Robert Mugabe's regime."
Zimbabwe's leading millers - National Foods, Blue Ribbon and Victoria Foods - have shut production at most of their mills because of the wheat shortage, according to AFP.
International aid agencies say about 4.3m out of Zimbabwe's 13m people will require food aid until the next harvest in May.
The country has suffered increasing food shortages, rising unemployment and runaway inflation since the government began redistributing seized white-owned farms six years ago.
Economists say the rate of inflation could reach 1,000% by April.