Pope Leo lamented during an event in Angola on Monday that many people in the world were being "exploited by authoritarians and defrauded by the rich", the latest example of a forceful new speaking style he has adopted on his four-nation Africa tour.

The first US pope, who has drawn the ire of President Donald Trump with his more outspoken comments, told worshippers at a Mass in Saurimo, near the Democratic Republic of Congo border, that violence and oppression went against the Christian message.

"Every form of oppression, violence, exploitation and dishonesty negates the resurrection of Christ," said the pontiff, referring to the core belief of Christianity that Jesus rose from the dead after being crucified.

His visit to Angola marks the third leg of an ambitious 10-day Africa tour, one of the most complicated ever conducted by a pope, with stops in 11 cities and towns in four countries, traversing nearly 18 000 km over 18 flights.

Leo, who became the head of the 1.4-billion-member Catholic Church last May, kept a relatively low profile in the first 10 months of his papacy but has issued forceful denunciations of war and inequality during his Africa tour.

He has also repeatedly criticised world leaders, without naming individuals.

On Saturday the 70-year-old pontiff decried exploitation of natural resources in Africa by "despots and tyrants". Last Thursday he said the world was "being ravaged by a handful of tyrants".

The pope told journalists on Sunday that his speeches during the tour were written weeks ago and not aimed directly at Trump. He has strongly criticised the US and Israeli attacks on Iran, which began on February 28.

ENTHUSIASTIC CROWDS

Crowds in Angola, where 80% of the population identifies as Christian - and about half of them as Catholic - have been enthusiastic for Leo, with people lining streets along his routes and dancing and screaming to greet him.

Two events on Sunday, a Mass attended by throngs in a dirt field and a prayer at a site that was once a hub for transatlantic slavery, drew roughly 130 000 people.    

Monday is Leo's last full day in Angola. He heads on Tuesday to Equatorial Guinea, the final leg of his Africa tour. 

He will give a speech there to the country's political leaders after meeting with President Teodoro Obiang Nguema Mbasogo, who has been in power since 1979, making him the world's longest-serving president.

Equatorial Guinea is widely criticised as one of the most repressive countries in the region. The government denies allegations of human rights abuses and corruption.