The death of Victor Santisteban Yacsavilca, 55, in Lima brings to 58 the nationwide toll in the protests that began in early December after the impeachment and arrest of President Pedro Castillo.
Initially focused in Peru's rural, mountainous south, protests have gained steam in the capital in recent weeks.
Saturday's protests were mostly in Lima and the southern Cusco region, Peru's ombudsman said in a statement.
Santisteban had suffered a severe head injury, the national health insurance agency said.
Some protests escalated as demonstrators armed with rocks and makeshift shields clashed with police, who deployed gas and rubber bullets.
Peru's ombudsman condemned reports of attacks against journalists covering the protests.
President Dina Boluarte expressed regret early on Saturday after Congress refused to speed up the timeline for a presidential election amid the unrest, her office said.
Lawmakers had given an initial green light to moving elections from 2026 to 2024, but on Friday voted down proposals hold the election this year.
Boluarte has repeatedly backed moving up elections as she struggles to quell the protests calling for her resignation.
Congress will continue debate on Monday.
On Friday Boluarte said an election could happen this year.
"We urge lawmakers to put down their partisan and group interests and put the interest of Peru first. Our citizens promptly await a clear response that will pave a way out of the political crisis and build social peace," Boluarte's office said on Twitter.
Boluarte, who took office after Castillo's removal, has maintained she will stay on as president until elections are held.
