Striking workers making shoes and clothes for Western brands have blocked roads and briefly scuffled with police in Cambodia.

The workers are demanding a two-fold increase in the minimum wage to $160.

The protests Friday snarled traffic in and around the capital Phnom Penh.

Human rights activist Om Sam Ath said protesters blocking a highway leading to Sihanoukville throw stones at police, who fired into the air.

He said four workers were injured, but it was unclear how serious the injuries were.

Most of the country's 500 factories have been closed since Thursday, when the manufacturers association urged its members to cease operations, citing the fear of violence.

The garment industry employs more than 500,000 people and is Cambodia's biggest export earner.