Peru has declared a state of emergency in the country's south after a fourth person was killed in a demonstration opposing a copper-mining project.

Cabinet chief Pedro Cateriano said a 60-day emergency would take effect in the Tambo valley on Saturday, as troops were being ordered into the streets to support more than 2,000 police.

The suspended rights would include freedom of assembly, freedom of movement and protection warrant-less searches.

The move, which means the military will take charge of security in the province of Islay, came after clashes between protesters and the police left a 55-year-old demonstrator dead and four others injured.

Witnesses told the AFP news agency that the victim died after he was shot in the chest. Local authorities did not confirm or deny the information.

Protests have escalated since farmers mounted resistance two months ago to the $1.4m project owned by Southern Copper, a subsidiary of Grupo Mexico.

Backed by local mayors, residents of the 40,000-population valley fear the open-pit mine will pollute their water and contaminate their crops.

The mining company claims it will use desalinated water from the nearby Pacific Ocean in processing and pipe it back to the sea.

Peru, which has significant mineral wealth, is the third largest copper producer and 62 percent of its export revenues come from mining.

The government last declared a state of emergency in 2012 after protests against the Conga gold mining project in the northern region of Cajamarca claimed five lives.

Source: Agencies