Pope Leo arrived on Tuesday in Equatorial Guinea, led by the world's longest-serving president, for the final leg of a four-nation Africa tour during which the pontiff has issued sharp denunciations of despotism and inequality.

Leo, who has drawn the ire of President Donald Trump with his more outspoken comments, arrived from Angola, where on Monday he lamented that many people globally were being "exploited by authoritarians and defrauded by the rich." 

His statements were the latest evidence of a forceful new speaking style he has embraced while in Africa.

On the flight from Angola to Malabo, on the island of Bioko in the Gulf of Guinea, Leo paid respects to his predecessor, Pope Francis, who died one year ago today.

He was scheduled to give a speech to political leaders after meeting with President Teodoro Obiang Nguema Mbasogo, who has been in power since 1979, three years before the Central African country's only other papal visit, by Pope John Paul II in 1982.

Leo's arrival "presents a profound opportunity to affirm, clearly and convincingly, that human dignity, justice, and accountability are not optional, but essential responsibilities of governance," Tutu Alicante, a US-based human rights lawyer and activist from Equatorial Guinea, told Reuters.

More than 70% of the country's population of 1.8-million identify as Catholic.

Obiang, whose government oversaw a now-declining oil boom that began in the 1990s, has been widely criticised as one of the most repressive leaders in the region.

He denies allegations of human rights abuses and corruption.

Leo, who spent decades as a missionary in Peru before becoming pope, is expected to speak Spanish throughout his two-day visit to the former Portuguese and Spanish colony.

POPE TO VISIT PRISON, BLAST SITE

The pope is undertaking an ambitious 10-day Africa tour, one of the most complicated ever conducted by a Catholic leader, with stops in 11 cities and towns in four countries, traversing nearly 18 000 km over 18 flights.

Wednesday will be the most intense day of the tour, with the pope taking three flights to visit three cities across Equatorial Guinea. 

In Bata, the pope will visit a high-security detention centre that Amnesty International has said is one of three notorious facilities in the country where detainees, including political prisoners, are regularly held for years without access to lawyers or their families. 

The government dismisses criticism of its justice system and says it has an open democracy.    

Alicante said that while some facilities had been spruced up ahead of Leo's arrival, there remained a need for comprehensive, lasting reforms.

"The real test will be whether humane conditions, access to medical care, and basic rights are sustained long after the papal visit concludes," he said.

Leo will also pray in Bata at the site of a series of explosions in 2021 at a military barracks that killed more than 100 people, which the government blamed on poor storage of ordnance. 

Human rights activists have called for an independent investigation into the incident, so far in vain.