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 rising 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 costs $66,000 Zimbabwean (55 cent), having risen 30% in just one week.

Mugabe denies his land reform programme has contributed to the crisis, blaming 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.

International aid agencies say about 4.3 million of Zimbabwe's 13 million people will require food aid until the next harvest in May.