Farmer Mohammad Agha inspects his crop

Tractors were used to chew up the fields, officials said.

"Our work is going on and we will keep destroying poppy crops until they are completely finished," a spokesman for the Helmand governor told the Afghan Islamic Press.

On Tuesday protesting farmers blocked a key road from Pakistan, preventing thousands of Afghan refugees from returning home.

Profitable crop

Government officials sent to the main poppy growing areas of eastern and southern Afghanistan have come under attack.

They have been offering the farmers about $250 per acre to destroy their poppy crops.

The government has now raised the offer to $350.

After the fall of the Taleban, many farmers borrowed money to plant poppies - one of the few profitable crops in the region.

Some refugees are more enthusiastic than others

The farmers still have to pay back the cash. They say the compensation being offered by the government is derisory.

Some have shot at government officials and burned their cars.

Before the Taleban banned poppy growing, Afghanistan supplied 90% of the world's heroin.

A BBC correspondent in Afghanistan says that if the Afghan Government cannot fulfil its promise to eradicate the poppy, it risks losing some of the goodwill of the West, which is helping pay to have the crop destroyed.

The Afghan authorities have now asked for more international help in targeting the poppy crops.