This was the deadliest day so far of protests demanding early elections and the release of jailed former president Pedro Castillo.
The clashes occurred in Juliaca, a city near the banks of Lake Titicaca in southern Peru's Puno region, and left 68 people injured, Henry Rebaza, a Puno health ministry official, told the state-run television channel TV Peru.
The dead included at least two teenagers, according to the ministry.
Some of the bodies had bullet wounds, Puno's regional health director, Ismael Cornejo, told local radio station RPP.
The latest casualties raise the death toll from anti-government clashes with security forces to 39 since the protests began in early December following the removal and arrest of Castillo shortly after he tried to illegally dissolve Congress.
According to Reuters, Castillo is serving 18 months of pre-trial detention on charges of rebellion, which he denies.
MP/PR