The Pope's visit to Chile has been hit by protests over a Catholic priest child sex abuse scandal. Nine churches have been firebombed in the past week, and scores of demonstrators were arrested during his first open-air mass in Santiago.

Pope in Chile
Police detain a protester dressed as a nun during the arrival of Pope Francis in Santiago Carlos Vera/Reuters

Pope Francis opened his visit by diving head-first into the scandal, begging for forgiveness for the "irreparable damage" done to children who were raped and molested by priests.

In his first event of the day, Francis met privately with Chilean President Michelle Bachelet and then addressed politicians, judges and other authorities at La Moneda palace. They interrupted him with applause when he said he felt "bound to express my pain and shame" that some of Chile's pastors had sexually abused children in their care.

Francis didn't refer by name to Chile's most notorious paedophile priest, the Rev Fernando Karadima, who was sanctioned in 2011 by the Vatican to a lifetime of "penance and prayer" for sexually molesting minors. Nor did he refer to the fact that the emeritus archbishop of Santiago, a top papal adviser, has acknowledged he knew of complaints against Karadima but didn't remove him from ministry.

Karadima had been a politically connected, charismatic and powerful priest who ministered to a wealthy Santiago community and produced dozens of priestly vocations and five bishops.

Victims went public with their accusations in 2010, after complaining for years to church authorities that Karadima would kiss and fondle them when they were teenagers.

While the scandal rocked the church, many Chileans are still furious over Francis' subsequent decision, in 2015, to appoint a Karadima protege as bishop of the southern city of Osorno. Bishop Juan Barros has denied knowing about Karadima's abuse but many Chileans don't believe him, and his appointment has badly split the diocese.

At a protest near O'Higgins park where Francis celebrated Mass, police fired tear gas and water cannons before detaining several dozen demonstrators. Protesters carried signs with messages reading "Burn, pope!" and "Paedophile accomplice".

Despite the scandal, many Chileans are excited to see the pope. Thousands lined the streets of Santiago to get a glimpse of Francis after he arrived, though the crowds were notably thin compared to previous visits to other Latin American capitals.

An estimated 400,000 jubilant Chileans turned out in droves for his first public Mass, a massive gathering in O'Higgins park where St John Paul II celebrated Mass three decades ago. Before the service began, Francis took a long, looping ride in his popemobile through the grounds to greet well-wishers, some of whom had camped out overnight to secure a spot.

While not causing any injuries, the nine church fire-bombings in the past few days have marked an unprecedented level of protest against history's first Latin American pope on his home turf.