The cause of the cable failures was not immediately clear.
Ivory Coast was experiencing a severe outage, while Liberia, Benin, Ghana and Burkina Faso were seeing a high impact, Netblocks's data showed.
Internet firm Cloudflare said on one of its X accounts that monitors trends that major internet disruptions were ongoing in Gambia, Guinea, Liberia, Ivory Coast, Ghana, Benin and Niger.
"There seems to be a pattern in the timing of the disruptions, impacting from the north to the south of Africa," Cloudflare Radar said.
South African telecoms operator Vodacom also blamed connectivity issues on undersea cable failures affecting the country's network providers.
(Reporting by Anait Miridzhanian and Ngouda Dione; Editing by Hugh Lawson and Alex Richardson)
