Zimbabwe's main bread producer has warned it only has two days' supply of flour, state media have reported.
Bread shortages could further boost inflation
The company, Lobels Bread, said a flour shortage had already forced it to scale back its operations by 80%.
Reports say 36,000 tonnes of imported wheat are blocked in a Mozambican port owing to foreign exchange shortages.
A foreign currency crisis caused inflation to rise to 7,638% in July. Government price controls have been blamed for worsening shortages.
Lobels' operations director, Lemmy Chikomo, said stocks would run out after two days if they were to cease production.
He said the firm could only guarantee 40,000 loaves of bread per day, as opposed to 200,000 previously.
Critics have blamed President Mugabe's policies, especially the seizure of farms, for ordinary Zimbabweans' hardship.
For his part, President Mugabe has accused foreign governments of trying to interfere in Zimbabwe's affairs - saying some businesses had raised prices without justification as part of a Western plot to oust him.