In the southwestern region of Arequipa, a bus plunged into a ravine 100 meters (328 feet) deep, killing 10 passengers and wounding 30 more.
The bus, operated by the Lomas del Sur company, crashed around dawn while traveling between the towns of Ocona and Camana.
The other accident, late Friday in the southeastern region of Puno, left nine people dead and ten wounded after a minibus collided head-on with a truck on the road between Juliaca and Putina, some 3,800 meters (12,400 feet) above sea level.
Fatal road accidents are common in Peru, in part because of lax traffic enforcement but also because of the country's challenging mountain terrain, with its many sharp curves and steep precipices.
More than 2,500 people were killed in road accidents in 2013, according to official statistics.