Pope Francis denounced the "poison of greed" driving conflicts in Africa as he began a visit to Democratic Republic of Congo on Tuesday, saying the rich world had to realise that people were more precious than the minerals in the earth beneath them.

Many tens of thousands of people cheered as he travelled from the airport into the capital Kinshasa in his popemobile, with some breaking away to chase it while others chanted and waved flags.

But the joyous mood, one of the most vibrant welcomes of his foreign trips, turned sombre when the 86-year-old pope spoke to dignitaries at the presidential palace. He condemned "terrible forms of exploitation, unworthy of humanity" in Congo, where vast mineral wealth has fuelled war, displacement and hunger.

"Hands off the Democratic Republic of the Congo. Hands off Africa. Stop choking Africa: it is not a mine to be stripped or a terrain to be plundered," Francis said.

Congo has some of the world's richest deposits of diamonds, gold, copper, cobalt, tin, tantalum and lithium, but those have stoked conflict between militias, government troops and foreign invaders. Mining has also been linked to inhumane exploitation of workers, including children, and environmental degradation.

"It is a tragedy that these lands, and more generally the whole African continent, continue to endure various forms of exploitation," the pope said, reading his speech in Italian while seated. People listening to a French translation applauded repeatedly.

"The poison of greed has smeared its diamonds with blood," he said, referring to Congo specifically.

Compounding the country's problems, eastern Congo has been plagued by violence connected to the long and complex fallout from the 1994 genocide in neighbouring Rwanda.

Congo accuses Rwanda of backing the M23 rebel group fighting government troops in the east. Rwanda denies this.

"As well as armed militias, foreign powers hungry for the minerals in our soil commit, with the direct and cowardly support of our neighbour Rwanda, cruel atrocities," Congolese President Felix Tshisekedi said, speaking just before the pope on the same stage on a hot, muggy afternoon.

The pope did not name Rwanda in his address or take sides in the dispute.

Rwandan government spokesperson Yolande Makolo rebuffed Tshisekedi's comments. "It’s obvious that this ridiculous obsession with scapegoating Rwanda is President Tshisekedi’s electoral strategy - a distraction from the poor performance of his government, and failure to deliver to their citizens," she told Reuters.

'Devoured by violence'

An estimated 5.7 million people are internally displaced in Congo and 26 million face severe hunger, largely because of the impact of armed conflict, according to the United Nations.

About half of Congo's population of 90 million are Roman Catholics and the Church plays a crucial role in running schools and health facilities in the sprawling central African country, as well as promoting democracy.

The pope criticised rich countries for ignoring the tragedies unfolding in Congo and elsewhere in Africa.

"One has the impression that the international community has practically resigned itself to the violence devouring it (Congo). We cannot grow accustomed to the bloodshed that has marked this country for decades, causing millions of deaths," he said.

Tshisekedi made a similar point: "While the international community has remained passive and silent, more than 10 million people have been horribly killed."

First scheduled for last July, the pope's trip was postponed because of a flare-up of a chronic knee ailment. Francis had originally planned to travel to Goma, in eastern Congo, but that stop was scrapped because of a resurgence in fighting between M23 rebels and government troops.

In an apparent reference to the M23 and other militias active in Congo's eastern regions, the pope said the Congolese people were fighting to preserve their territorial integrity "against deplorable attempts to fragment the country".

On Wednesday, Francis will celebrate Mass at a Kinshasa airport that is expected to draw more than a million people. He also will meet victims of violence from the east.

Francis will stay in Kinshasa until Friday morning, when he will fly to South Sudan, another African country grappling with conflict and poverty.

In a first, he will be accompanied for that leg of his journey by the Archbishop of Canterbury, leader of the global Anglican Communion, and by the Church of Scotland Moderator. The religious leaders have described their joint visit as a "pilgrimage of peace" to the world's youngest nation.

South Sudan gained independence in 2011 from predominantly Muslim Sudan after decades of conflict. Two years later inter-ethnic conflict spiralled into a civil war that killed 400,000 people. A 2018 deal stopped the worst of the fighting.