Protesters have vandalised several Catholic churches in Chile in the face of Pope Francis' visit to the country next week, and warned they will target the Catholic leader with a "bomb".

Demonstrators used firebombs to attack four churches in the capital Santiago on Friday, leaving behind a note warning the pope: "The next bomb will be in your robe," according to Latin American broadcaster Telesur.

Authorities have said they are investigating the incidents, which caused no injuries, though they have yet to make any arrests.

Chilean President Michelle Bachelet described the attacks as "very strange" and said authorities had been unable to tie the incidents to a "particular group" so far, Telesur reported.

"In a democracy, people can express themselves as long as it's done in a pacifist way," she said, and called for a "climate of respect" during the pope's upcoming visit.

Other pamphlets left by the attackers called for "autonomy and resistance" from Chile's indigenous Mapuche people, according to the Catholic News Agency.

Roughly two-thirds of Chile's 1.5 million Mapuches live in squalor in urban areas, and the remainder in poor rural communities. They are the country's poorest and most marginalised segment of society.

Condemnation of attacks

Sebastian Pinera, Chile's president-elect, condemned the attacks in a statement on Twitter.

"The hatred and intolerance cannot prevail above the respect and the rule of law," he said on Friday.

Pinera added that Chile would receive the pope "with joy and peace".

Condeno los actos de violencia contra Iglesias de Peñalolén, Estación Central y Recoleta esta madrugada. El odio y la intolerancia no pueden primar por sobre el respeto y el Estado de Derecho. Recibamos al Papa Francisco con alegría y en paz. — Sebastian Piñera (@sebastianpinera) January 12, 2018

Pope Francis, the first Latin American pope, is due to arrive in Chile on Monday.

He is scheduled to hold mass on Tuesday in a Santiago park, with hundreds of thousands of people predicted to attend.

His visit is expected to be met with protests on a range of issues, including the rights of Chile's indigenous people and an ongoing sexual abuse scandal in the Catholic Church.

The pontiff, born in Argentina, will also visit the Chilean cities of Temuco, where he is expected to meet Mapuches, and Iquique, before travelling to Peru.