Pope Benedict XVI has urged Catholics in Angola to woo people "living in fear of spirits" into the church.
In a Mass celebrated in Angola's capital, Luanda, he said Catholics should reach out to those who believe in witchcraft and spirits.
Human rights groups say many children in Angola have been abused after being accused of possession by spirits.
The pontiff, who arrived in Angola from Cameroon on Friday, is on the last stop of his week-long African tour.
He will later meet youths at a city football stadium.
On Friday, he made a powerful attack on corruption, which analysts say is rife in oil-rich Angola.
The climax of the visit will be on Sunday, when two million people are expected to hear the Pope address an outdoor service.
The Pope urged Angola's Catholics to reach out to those who had joined the burgeoning number of sects.
"Today it is up to you, brothers and sisters, following in the footsteps of those heroic and holy heralds of God, to offer the risen Christ to your fellow citizens," the Pope said to 1,500 Angolan clergy and laypeople at Luanda's Sao Paulo church.
"In today's Angola, Catholics should offer the message of Christ to the many who live in the fear of spirits, of evil powers by whom they feel threatened, disoriented, even reaching the point of condemning street children and even the most elderly because - they say - they are sorcerers," he said.
Belief in witchcraft has spread rapidly in some parts of central and southern Africa, including Angola, over the last few years, say analysts.
Thousands of people lined the streets of Luanda to cheer the Pope as he travelled in the Popemobile through the capital after the Mass.
After arriving in Angola on Friday, the 81-year-old pontiff spoke out against corruption.
In a televised address, the Pope said that Africans needed "a firm determination to change hearts and finally put a stop, once and for all, to corruption".
Benedict's speech was echoed by President Jose Eduardo dos Santos, who has been Angola's leader for the past three decades and through a civil war which has left hundreds of thousands dead.
Mr dos Santos' party won elections last year that critics said were marred by fraud and corruption.
Angola, a former Portuguese colony, is rich in diamonds and oil, but war has left most of its people in poverty.
The Pope sparked controversy earlier on his tour for remarks refusing to advocate condoms as a way to help stop HIV/Aids, prompting France, the Netherlands and even the pontiff's native Germany to express concern.
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