Zimbabwe's central bank has introduced 500 million Zimbabwe dollar notes worth just $A2.15 in the latest sign of spiralling hyperinflation, only a week after issuing the 250 million bill.

The new highest denomination note would buy about two loaves of bread.

The central bank also introduced special agricultural cheques in five billion, 25 billion and 50 billion Zimbabwe dollar denominations to facilitate payments to farmers during the current selling season.

Farmers normally have to carry huge stacks of bank notes after selling their produce to state agencies, while consumers often carry large piles of cash with them for simple daily transactions.

The country is currently in the middle of the tobacco and maize marketing season.

"The Reserve Bank of Zimbabwe is pleased to announce the introduction of special instruments to cater for the marketing needs of our farmers in the form of 'special agro cheques' whose lifespan will run through December 31 2008," the central bank said in a statement.

It said the cheques were freely tradeable and would start circulating on Tuesday, while the new currency notes are available immediately.

Zimbabwe, which has the highest inflation rate in the world at around 165,000 percent, has been beset by long queues at banks as consumers seek bank notes to stock up on basic goods, the prices of which are constantly rising.

Zimbabweans had hoped elections on March 29 could help put an end to the country's economic meltdown, which has also led to 80 per cent unemployment, chronic food and fuel shortages, and a flood of refugees to neighbouring states.

But the parliamentary election results have been disputed, and a run-off for the presidency has been delayed and is now due to take place by the end of July.

- Reuters