President Ernest Bai Koroma fought back tears as he described the devastation during a press conference in the hard-hit hilltop town of Regent, east of the capital.

"Entire communities have been wiped out," he said. "We need urgent support now."

Rescue workers have been searching for survivors amid the hundreds of homes that were engulfed by mud when a mountainside collapsed early Monday. The disaster came after three days of heavy rains and struck when many people were still sleeping in their beds.

President Koroma urged residents of flooded areas to evacuate immediately to make way for military personnel and other rescue workers combing through the debris.

Chief coroner Seneh Dumbuya told the Reuters news agency that nearly 400 bodies had been recovered so far, and that he expected the death toll to pass 500 as the search continued.

Fears for hundreds still missing

Authorities were preparing to bury the bodies in four different cemeteries across Freetown on Wednesday to relieve pressure on the city's already overwhelmed morgues, Idalia Amaya, an emergency response coordinator for Catholic Relief Services, said.

The Red Cross estimates that some 600 people are still missing and that around 3,000 are homeless and in need of shelter, food and medical assistance.

"We are also fearful of outbreaks of diseases such as cholera and typhoid," Red Cross Society spokesman Abu Bakarr Tarawallie told the Thomson Reuters Foundation. "We can only hope that this does not happen."

The city of around a million people often experiences flooding during the annual rainy season, when there's a spike in the risk of potentially deadly waterborne diseases.

Britain's aid department said it is sending assistance, with International Development Secretary Priti Patel saying she was "deeply saddened" by the devastation.

Israel's foreign ministry said it would also provide "assistance immediately and in every way possible" including clean water, medicines and blankets.

nm/jm (Reuters, AP, AFP)