Cambodian police fired live ammunition at protesting garment workers outside the capital Phnom Penh, killing a bystander and injuring at least six protesters.

Human rights group Licadho said that hundreds of workers from the SL Garment Processing factory clashed with about 1,000 riot police who had been sent to block a march to the residence of Prime Minister Hun Sen.

The factory makes clothing for Gap, H&M and other international brands.

Licadho spokesman Am Sam Ath said that protesters had thrown rocks at the police, who responded with tear gas, rubber bullets and live ammunition.

"This is a cruel crackdown by the authorities," he said at a city hospital where the injured were taken.

Five people had suffered gunshot wounds in addition to a bystander named by her family as Eng Sokhom, who was killed after being struck by a bullet while selling rice by the roadside.

Workers from the factory have been protesting for months, calling for better working conditions and pay.

Their unions said that the violence broke out when riot police stopped the workers, who have been demonstrating periodically for weeks.

"The workers went to the prime minister to seek his intervention to improve the working conditions at the factory.

"But the authorities used weapons to crack down on them," said the Coalition of Cambodian Apparel Workers Democratic Union deputy leader Kong Athit.

He said eight people had been injured either by bullets or by police beatings after nearby residents and Buddhist monks joined the workers' protest.

Hundreds of riot police armed with batons and shields remained on the capital's streets, which were littered with rocks and tear gas canisters, after the protesters were dispersed.

The multibillion-pound garment industry employs about 650,000 people.

Workers earn about £69 a month with overtime.

The International Labour Organisation had accused Cambodia of backsliding in efforts to improve working conditions in the sector and failing to make progress in safety and the use of child labour.