Inflation in Zimbabwe is now running at 600 per cent and the government is reported to have put security forces on alert as public discontent rises.
Shortages of wheat could force bakers to import flour fro South Africa, leading to further price rises.
Zimbabwe has been in economic decline since President Robert Mugabe began seizing white-owned farms in 2000.
He has denied that his land reform program has contributed to the current crisis.
Zimbabwe's opposition party, Movement for Democratic Change, said the situation is becoming unbearable.
International aid agencies say about four million people in Zimbabwe, a third of the population, will require food aid to get them through to the next harvest in May.