In contrast Sudan, Equatorial Guinea and Libya require all African visitors to have visas before travel.

While the researchers found that overall openness when it comes to visa regimes is improving, almost half of the continent’s more than 50 countries still impose visa restrictions on citizens of at least one other African nation.

The index is produced jointly by the African Union and the African Development Bank. They note that in order for the fledgling Africa Continental Free Trade Area to succeed, non-tariff barriers, such as visa restrictions, need to be dismantled.

Applying for a visa can be costly and time-consuming for anyone wishing to trade with or study in another African country.

"We need to break down all barriers that impede the free movement of people across the continent, especially that of workers. This is vital for promoting investment," the head of the African Development Bank Akinwumi Adesina said at the launch of the report.