Key facts about the Catholic religion in the Philippines as one of its biggest annual events, the Feast of the Black Nazarene is held on Monday.

NUMBERS: About eight in 10 Filipinos are Catholic, making the nation of more than 100 million people Asia's bastion of Christianity. There are many other popular Christian denominations, including a powerful homegrown group called Iglesia ni Cristo. Muslims make up about 5.6 percent of the population, government figures say.

HISTORY: Portuguese explorer Ferdinand Magellan claimed the islands for Spain in 1521 on a voyage to circumnavigate the globe. The archipelago was named after the Spanish monarch King Philip II. Spanish rulers and friars entrenched Catholicism, over what had been mainly polytheist, animist and Muslim populations during nearly 400 years of colonial rule that ended when the Americans wrested control in 1898.

UNIQUE WORSHIPPING: Filipino Catholics are known for enormous, colourful and in some cases extreme expressions of piety.

Thousands of barefoot devotees join the religious procession in Manila each January hoping to touch a centuries-old icon of Jesus Christ, called the Black Nazarene, which is believed to have miraculous powers.

Other extreme forms of worship include Easter devotees who whip their backs bloody while others have their hands nailed to crosses in all-too-real imitations of Christ's passion on Good Friday.

POLITICAL POWER: The largely conservative local church became an agent for change when it opposed then-president Ferdinand Marcos' martial rule in 1972-1981. It then helped to lead a bloodless "people power" revolt that ended his 20-year reign in 1986. However its influence has waned in recent years with the recently elected President Rodrigo Duterte openly mocking Church figures who criticise his policies.

INFLUENCE ON LAWS: Church lobbying has helped to ensure the Philippines remains the only state in the world aside from the Vatican where divorce remains illegal. Abortion and same sex marriage are also outlawed.

MODERNISING VALUES: The Church led a long but ultimately failed campaign against artificial birth control. It ended with a law, passed in 2012, requiring the state to supply condoms and birth control pills, as well as provide sex education in schools. Duterte has vowed to expand the programme.

Many Filipinos also ignore the Church on key family value issues, with hundreds of thousands of women having illegal abortions each year. Many people also live together without getting married. Others in unhappy marriages deeply resent the Church for preventing divorce.

SAINTS: The Philippines has two saints, both martyred while spreading the faith to the rest of the region: The first is San Lorenzo Ruiz, killed in Japan in 1637 and canonised in 1987. The other is San Pedro Calungsod, a catechist who was killed in Guam in 1672 and canonised in 2012.

PAPAL VISITS: In 1970 Pope Paul VI became the first pontiff to visit the country. He survived a knife attack by a Bolivian painter dressed as a priest. The attacker was subdued and the visit proceeded without further incident.

Pope John Paul II visited in 1981 and again in 1995. On the latter visit, an estimated five million people attended a mass in Manila's central park that was at that time the world's biggest papal crowd.

That record was broken in January 2016 when an estimated six million people gathered at the same park for an open-air mass by Pope Francis.