From the dusty southern reaches of the Sahara to the lush uplands of central Angola, the Roman Catholic church is on the move in Africa, a continent that may be home to as many as half a billion Catholics by the middle of the century.

Since 1980, the number of Catholics in Africa has risen more than three-fold - to nearly 200 million by 2012 - according to the Center for Applied Research in the Apostolate (CARA), a unit affiliated with Washington's Georgetown University.

Its success is not purely a function of Africa's high birth rates and gradually increasing life expectancy.

CARA estimates that over that same period, the proportion of Catholics in Africa's population rose to 18.6 percent from 12.5 percent.

It is with such numbers in mind that Pope Francis makes his first papal visit to the continent this month, stopping off in Kenya, Uganda and Central African Republic, a deeply impoverished country where dozens of people have been killed in clashes this year between Christians and Muslims.

However, numbers alone do not tell the whole story.

In cities, towns and villages across sub-Saharan Africa, where worshippers gather in venues as diverse as an ornate cathedral in Nairobi to a roadside cross on the outskirts of Kampala, the Catholic church is facing serious competition.

Besides Islam - now the religion of almost one in three Africans - it is coming up against a host of Pentecostalist and evangelical churches fitting into many Africans' love of music, dance and free-form self-expression.

In some instances, the relatively rigid nature of established Christian churches, both Roman Catholic and Anglican, are of limited appeal to Africa's overwhelmingly young church-going population, experts say.

"These (evangelical) churches are quite good at tapping into traditional African sensitivities of giving expression to whatever you feel in a very bubbly manner," said Christo Lombaard, a professor of Christian spirituality at the University of South Africa in Pretoria.

"They're not like these very staid churches that I grew up with."

For a Reuters photo essay on "Catholicism in Africa", click here.