By Marco Aquino

LIMA (Reuters) -Tens of thousands of protesters took to the streets in Peru on Wednesday in marches organized by groups opposed to President Dina Boluarte, while police took anti-riot measures against some demonstrators, arresting at least six.

Peaceful protesters affiliated with left-wing groups and unions marched in the capital Lima, while isolated incidents involving the police were reported in an Andean region linked to past social conflicts, media reported.

"We want justice, peace and calm, and that Boluarte leaves immediately," said protester Dionisio Flores in Lima.

Many Peruvians accuse Boluarte and her allies of illegitimately removing and jailing her leftist predecessor Pedro Castillo, which led to sometimes violent protests through March in which 67 people were killed.

By late evening, six civilians and two police officers had been injured as protesters carrying rocks and bottles squared off with security forces who resorted to tear gas, the ombudsman said.

"The protests may continue tomorrow," Interior Minister Vicente Romero told a press conference, adding that six protesters had been arrested.

Some 21,000 people took part in the marches, Romero said, though he added that some people were taking part to press on issues unrelated to the protesters' main demands.

The unrest is also fueled by longstanding anger over widespread poverty and deep inequality that has persisted even as the major copper-producing nation has grown wealthier.

Peru, the second-largest supplier of the metal globally, could also face disruption along its key mining corridor, where Castillo is popular and many communities support the protests.

Apart from Boluarte's removal, many protesters also want the right-wing Congress dissolved, elections, and a new constitution.

"This government is immoral, incompetent," said Martha Manami, who attended one of the marches. "It has used the armed forces to suppress us."

Some 24,000 police officers were deployed throughout the country in the lead up to the protests, officials said.

Transport officials said protesters blocked at least eight highways, most in the southern Arequipa and Cusco regions. They were open again by the evening, authorities said.

"We will respect the right of people to protest, but if these turn violent we will make rational use of force to impose authority," Lima police chief Roger Perez told reporters.

Jorge Pizarro, a spokesperson for one of the protest organizers, said demonstrators "will not seek a confrontation with the police."

But in the Andean town of Huancavelica, protesters set the door of a government building ablaze. Police doused it and then dispersed the crowd with tear gas, a television station reported.

(Reporting by Marco Aquino; Writing by Sarah Morland; Editing by Alexander Villegas, Will Dunham, Josie Kao and Muralikumar Anantharaman)