By the BBC's Caroline Wyatt in Kabul

At least eight Afghan farmers have been killed and another 35 wounded during protests against the government campaign to eradicate their opium poppy crops.

I won't let them eradicate my field. I'll tell them I'll turn to thievery.

Farmer Abdul Samad

The protest began in the Kajaki district of the south-western province of Helmand, Afghanistan's biggest poppy growing area.

The farmers are angered at what they see as derisory compensation.

Afghan security men were ordered to fire on the protesters, most of them poor Afghan farmers, deeply unhappy with the government's plans to destroy their crops.

Twelve of the injured are reported to be in critical condition in hospital.

Compensation

This incident graphically illustrates how high tensions are running over the government's decree that this year's poppy harvest must be burnt.

Makeshift factories synthesise the heroin from opium sap

The Taleban managed to destroy most of last year's crops, but when it was defeated, many Afghan farmers took the chance to sow the poppies again.

They grow easily here, need little water and produce maximum profit.

The Afghan interim government has said it will pay compensation of $250 per acre to each farmer who destroys their crop, with much of that money being donated by the European Union.

But Afghan farmers say they can make up to $3,500 an acre from the poppies themselves.

They often borrow money from drug smugglers in advance to buy the seeds before being paid for the harvest.

Important test

The opium poppies themselves are already in full bloom in much of the south and west of Afghanistan.

Many farmers say they will defy the government's decree, despite the threat of having their land confiscated.

The interim government knows it will need to stop the drug supply at source to keep the good will of the West, where most of the heroin ends up.

However, this issue will undoubtedly be one of the biggest tests of the administration's authority.

If the crops aren't destroyed they will be refined to provide around 90% of the heroin in Britain and 70% of the world's supply.