AMNESTY International has called for an investigation into the killing of at least three people after police opened fire on striking garment workers in Cambodia.
The United States has also condemned the action of security forces and is urging restraint.
Striking workers, armed with sticks, rocks and petrol bombs, clashed with police in the Veng Sreng factory district in Phnom Penh over wages and conditions.
They have been demanding that the minimum wage be doubled to 160 dollars per month.
Amnesty says the government must hold the security forces to account, while the US state department has called for peaceful dialogue.
“Yesterday’s tragic violence must be investigated and those responsible for deaths and injuries held to account,” said Rupert Abbott, Amnesty International’s Cambodia researcher.
Mr Abbott says the Cambodian government needs to rein in its security forces.
“Yesterday’s events sadly echo other recent incidents – on at least four occasions in the past few months, security forces have used unnecessary or excessive force, including live ammunition, against protesters and bystanders.”
Human rights advocates have called the crackdown the country’s worst state violence against civilians in more than a decade.
Half a million people work in Cambodia’s clothing industry – the country’s biggest export earner.