NAIROBI, Kenya (RNS) — When the doors swing open every Sunday morning, churches in Africa welcome thousands of new followers.

On this deeply religious continent, both Christianity and Islam are on the rise. But small groups of determined atheists are challenging Africa's grip on faith while seeking recognition and more followers.

Across Africa, groups have emerged stressing science and critical thinking as a better way of understanding the natural world.

One such group, Atheists in Kenya, has gained prominence and is now campaigning for a public holiday, Atheist Day, on February 17.

“We are asking the government to declare a public holiday as a way of raising awareness of atheism in Kenya,” said Harrison Mumia, the group’s president.

On the holiday, the group would convene “godless” parades while promoting freedom of religion and human rights in the East African country where more than 80 percent are Christians and about 10 percent are Muslims.

“We want to promote science and skepticism, and have an approach to morality that is rational and humanistic,” Mumia said.

Atheists in Nigeria are also becoming more vocal, pushing for public policies that are not influenced by religious belief but by critical thinking and science-based evidence.

“We have formed a legal body — the Atheist Society of Nigeria — to push for the vision of secular Nigeria,” said Calistus Igwilo, the group’s president.

Atheists have organized in most sub-Saharan African countries, including Ghana, South Africa, Zimbabwe and Uganda.

The groups say their numbers are on the rise, but membership is still relatively small.

Atheists in Kenya estimates it has 650 members in 2018, up from 60 in 2014, and boasts a social media following of more than 10,000. The Atheist Society of Nigeria counts about 5,000 members.

“This is quite remarkable, considering that very few atheists are willing to come out due to the stigma associated with being an atheist,” said Mumia.

Clerics and scholars are confident atheists will face an uphill battle in attracting a wider following. The future of Christianity lies in Africa, and by 2060, more than 4 in 10 Christians will call sub-Saharan Africa home, up from 26 percent in 2015, according to Pew Research Center.

In addition, 27 percent of all Muslims will live in sub-Saharan Africa by 2060, according to Pew. By contrast, atheists compose about 2 percent of the continent's population.

Jesse Mugambi, professor of philosophy and religious studies at the University of Nairobi, said atheism and agnosticism are shunned in traditional African thought.

“Many Kenyans consider Kenya to be a God-fearing country,” added Mumia. “Atheists are therefore considered devil worshippers.”

Some atheists have been laid off from work for refusing to participate in religious practices. Others are disowned by their families.

“They look quite strange (on) the continent where the concept of God spreads wide, even to the heart of African traditional communities,” said Wilybard Lagho, vicar general of the Catholic Archdiocese of Mombasa, in Kenya. “It is a very difficult task.”