People in West and Central Africa are experiencing problems connecting to the internet with Ivory Coast being the worst-affected country, the monitoring group NetBlocks reports.
It says that the companies operating the sub-sea cables linking the region to the internet are reporting multiple failures. But the exact cause of the problems is not clear, the Reuters news agency says.
NetBlocks says that the internet in Ivory Coast is operating at just 4% of its expected level.
Liberia, Benin, Ghana and Burkina Faso have also been badly affected, it reports.
Users in South Africa are also reporting slow speeds, website News24 says.
It quotes a spokesperson from telecoms company Vodacom saying that "multiple sub-sea cable failures between South Africa and Europe were impacting network providers".