Pope Francis admitted Monday he was frightened by the prospect of an accidental nuclear war as he headed for a weeklong visit to Chile and Peru.

"I think we are at the very edge," the pope told reporters aboard his plane when asked about the threat of a nuclear war in the wake of a recent string of tests by North Korea and a false missile alert last week that sparked panic in the US state of Hawaii.

"I am really afraid of this. One accident is enough to precipitate things," he said.

The pope set off from Rome's Fiumicino airport shortly before 9 am (0800 GMT) and is scheduled to arrive in Santiago at 8:10 pm (2310 GMT) on his first visit to Chile since becoming pope, and his sixth to Latin America.

The visit aims to bolster the local Church beset by child sex abuse scandals.

The 81-year-old Argentinian pontiff will find a very different Chile than the one he first encountered as a student priest in the 1960s.

Socialist President Michelle Bachelet has presided over major change in the once deeply conservative country, decriminalizing abortion, recognizing civil unions for same-sex couples and introducing a bill to legalize gay marriage.

The Catholic Church has been buffeted by the same winds of change, with numbers dropping to 67 percent, while the number of atheists has risen to 22 percent. Up to 90 percent of the population of neighboring Peru is Catholic.

Preparations for the visit have been overshadowed by a recent report that almost 80 members of the Chilean clergy have been accused of the sexual abuse of minors since 2000, more than half of them convicted by a Vatican court.

Protests are expected over Francis's appointment of a bishop in the southern city of Ororno who is accused of covering up for Fernando Karadima, an influential priest whom the Vatican convicted of abusing children in 2011.

"The Church has problems and is in the throes of trying to reaffirm itself, pointing to the need to strengthen the family and the rejection of abortion and homosexual marriage, but at the same time riven by internal problems, including priests who have been involved in sexual abuse," said University of Santiago sociologist Cristian Parker.

- Protests planned -

During his three days in Chile, Francis will meet with victims of the military dictatorship of Augusto Pinochet, while there are no formal plans to meet victims of pedophile priests.

Bachelet, who will meet Francis on Tuesday, has called on Chileans to welcome the pope, though a positive reception may not be universal.

 

On Friday, five Catholic Churches in the capital were attacked -- three of them with firebombs -- by what police said was an anarchist group. Demonstrations are planned by feminist and gay rights groups.

The highlight of the three-day visit will be an open-air mass in a Santiago city park on Tuesday.

At another mass at the airport in Temuco, the capital of the impoverished southern Araucania region, Francis is expected to draw attention on Wednesday to state persecution of the indigenous Mapuche people and also meet members of the community.

The Mapuche -- some seven percent of the Chilean population -- inhabited a vast territory before the arrival of Spanish colonists in 1541, and have long protested the loss of ancestral lands.

During his visit to Chile, the pope will also meet representatives of the poor and young people, as well as visit a women's prison.

The authorities expect an influx of nearly a million Argentines, Bolivians and Peruvians in Chile to see the pope.

Around 18,000 police and security forces have been mobilized for the pope, who has yet to visit his native Argentina almost five years into his papacy.

The pope will send greetings by telegram to the governments of Brazil, Paraguay and Argentina as his plane overflies their countries on its approach to Santiago.

On Thursday, the pope will travel to Iquique in the north of the country, where he will preside over another open-air mass, on the shores of the Pacific Ocean, before traveling on to Peru's capital Lima.

Peru is in the throes of a political crisis sparked by a controversial pardon for ex-president Alberto Fujimori, who was serving a 25-year sentence for human rights abuses, as well as another abuse scandal involving the clergy.