At least 179 people were killed in a mudslide near Sierra Leone's capital, Freetown, the Red Cross says.
A hillside in the Regent area collapsed early on Monday following heavy rains, leaving many houses covered in mud.
A BBC reporter at the scene says many people may have been asleep when the mudslide occurred.
Sierra Leone's Vice-President Victor Bockarie Foh said it was "likely that hundreds are lying dead". The total number of casualties is likely to rise.
Foh told Reuters news agency that the disaster was "so serious that I myself feel broken". He said that the area was being cordoned off as people were being evacuated, including many still feared trapped in their homes.
A spokesman for the Red Cross, Abu Bakarr Tarawallie, told the same news agency that 179 bodies were taken to the central morgue in Freetown.
Flooding is not unusual in Sierra Leone, where unsafe housing is regularly swept away by heavy rains.
In 2015, Freetown endured deadly floods sparked by monsoon rains that killed 10 people and left thousands more homeless.