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.

Several hundred thousand people in Maiduguri, which is the Borno state capital, have been forced from their homes by the floodwaters and at least 30 have died.