Ghana's army and navy have been called out to help after flash floods around Accra left 23 people dead.
The BBC's David Amanor in Accra says several people were swept away on Sunday night by rapidly rising waters while others were stranded on the roofs of their homes.
Transport links between the capital and other cities have been disrupted.
Much of the urban flooding has been blamed on the illegal construction of buildings on open drains and waterways.
"This is a disaster for the country as we have lost lives and property running into millions of cedis [Ghana's currency]," said National Disaster Management Organisation co-ordinator Kofi Portuphy.