The warning comes as Nigeria is already grappling with severe floods in northeastern Borno state where a dam burst its walls after heavy rains that have also caused floods in Cameroon, Chad, Mali and Niger - all part of Africa's Sahel region that usually receives little rain.

The Nigerian authorities say more than 270 inmates are now known to be missing after escaping from custody when severe flooding damaged a prison in the north-eastern city of Maiduguri. So far, seven are back in detention. The flooding was caused by the collapse of a dam following heavy rainfall.

Cameroon will initiate controlled water discharge releases starting 17 September 2023. The Nigeria Hydrological Services Agency has alerted Nigerians on the impending release of water from the Lagdo dam in Cameroon.