Merkel has been traveling with nearly a dozen German CEOs in Senegal and Ghana, two of Africa's fastest-growing economies. The tour aims to boost investment in a region that is a major source of migrants heading toward Europe, even as migrant arrivals across the Mediterranean are at their lowest level in five years.

Some in Europe hope that investing in West Africa will keep people in a region plagued with unemployment, rising extremism and the effects of climate change from leaving. Merkel's visit comes two days after that of British Prime Minister Theresa May, who announced a project with France to help Nigeria, the region's powerhouse, and neighboring Niger improve border cooperation along a key migration route.

The international community also has interest in sub-Saharan Africa's economic potential and its booming population, which is expected to double by 2050.

Nigeria is among several West African nations that in recent months have brought home thousands of citizens stranded in squalid camps in Libya on their way toward Europe. After reports of abuses, Buhari late last year called it appalling that some Nigerians "were being sold like goats for few dollars" in the North African nation.

Finding opportunity at home, however, has been a challenge. Some Nigerians were alarmed by recent reports based on data by the World Poverty Clock, funded by Germany's ministry for economic cooperation and development, saying their country had surpassed India with the largest number of people living in extreme poverty.

Also faced with widespread corruption, more than one-third of Nigerians say they have considered moving abroad, according to a 2017 Afrobarometer survey last year.