At least 300 people are reported to have died in mudslides and flooding near Sierra Leone's capital, Freetown.
The number of casualties is expected to keep rising, with hundreds of bodies trapped under the debris.
The worst-hit area is thought to be the Regent district, on the outskirts of Freetown, where dozens of houses were submerged when a hillside collapsed after heavy rains about 6am GMT (6pm NZT) on Monday.
It is understood whole families were buried alive as they slept, when a river of mud rushed through the town in the early hours of the morning.
Sierra Leone Vice-President Victor Bockarie Foh said it was "likely that hundreds are lying dead".
Mr Foh told Reuters that the disaster was "so serious that I myself feel broken". He said the area had to be cordoned off as people were evacuated, with many still feared trapped in their homes.
Locals were reportedly trying to recover bodies from the rubble and mud with their bare hands.
A Red Cross spokesperson said at least 205 bodies had been taken to the central morgue in Freetown, Reuters reports.
Another spokesman for the Red Cross, Abubakarr Tarawallie, told the BBC that the organisation's volunteers and staff had been involved in search and rescue operations and that people affected were in immediate need of shelter and blankets.
He added that at least 100 properties had been submerged and some had collapsed after a section of Sugar Loaf mountain came down before sunrise.
The AFP news agency later reported that the total death toll from flooding in and around the capital had risen to 312.
Hundreds of people are likely to be left homeless following the Regent mudslide.
Sierra Leonean disaster management official Candy Rogers said that "over 2000 people are homeless" as a result of the mudslide, AFP reported.
Mr Rogers said a huge humanitarian effort would be required to deal with the aftermath of the flooding.
Images posted on Twitter showed people wading through streets, waist-deep in muddy water, following the downpour in and around Freetown.
Flooding in Freetown, Sierra Leone pic.twitter.com/2g6zEVdkbC— Francis Reffell (@francisreffell) August 14, 2017
Flooding is not unusual in Sierra Leone, where unsafe housing in makeshift settlements can be swept away by heavy rains.
The rains often hit areas in and around Freetown, an overcrowded coastal city of more than one million people.
In 2015, Freetown endured deadly floods sparked by monsoon rains that killed 10 people and left thousands more homeless.
- BBC / RNZ