An Associated Press photographer and human rights workers said police fired rifles after several hundred workers blocking a road south of the capital Phnom Penh began burning tires and throwing objects at them. Several wounded workers could be seen after the shots were fired.
Chan Soveth of the human-rights group Adhoc said one person was killed and at least five wounded, but the death could not be immediately confirmed by officials or medical authorities.
The workers are part of a nationwide strike demanding a doubling of the monthly minimum wage to US$160. About 500,000 Cambodians are employed in the garment industry, the country's biggest export earner. The government has offered $100 a month.
On Thursday, Cambodian soldiers forcefully quelled a demonstration by garment factory workers who were striking for better pay, detaining Buddhist monks and labour leaders.
Soldiers from a military special command unit carrying metal pipes, knives, AK-47 rifles, slingshots and batons clashed with workers at a factory in an outlying area of Phnom Penh, local human rights group LICADHO said. Its statement said 10 people were taken into military custody and that monks and workers were beaten.
National Military Police spokesman Kheng Tito said those arrested had led hundreds of protesting workers in trying to destroy factory property by throwing stones and iron objects.
The violence comes at a time of political stress, as the opposition Cambodia National Rescue Party has protested daily for Prime Minister Hun Sen to step down and call new elections. Hun Sen won elections last July that extended his 28-year rule in the poor Southeast Asia country, but protesters led by opposition head Sam Rainsy accuse him of rigging the vote. Hun Sen has rejected their demand.
Although the wage and election issues are not directly linked, Cambodia's opposition has had long and close ties with the country's labour movement.
The workers represent a potent political force, because the garment industry is Cambodia's biggest export earner, employing about 500,000 people in garment and shoe factories. In 2012, the Southeast Asian country shipped more $4 billion worth of products to the United States and Europe.
On Sunday, many workers joined a massive political rally organised by the opposition.
The Garment Manufacturers Association in Cambodia has called for factory owners to close their plants, ostensibly for fear of damage by protesters. The situation puts pressure both on the workers, who go without pay, and the government, which relies on garment exports to power the economy.
In an evident effort to increase the pressure on Hun Sen, the association on Thursday sent a letter to the government asking that their members be allowed to export capital equipment to other countries, because they were unable to operate in Cambodia. There was no immediate response from the government.
LICADHO said that "The use of (military) Special Command Unit 911 to suppress demonstrations near Yak Jin factory in Phnom Penh's Pursenchey district is unprecedented and signals a disturbing new tactic by authorities to quash what have been largely peaceful protests."
"Some of those held are believed to have been severely beaten as they were arrested," it said.