NAIROBI (AFP) - A cargo train derailed in a sprawling Nairobi slum on Sunday, crashing into makeshift homes where scores of people are feared trapped, the Kenyan Red Cross said.

"One patient has been evacuated ... scores are feared trapped," the organisation said.

One of Africa's largest slums, Kibera's tin-roofed shacks are home to an estimated quarter of a million people, according to an NGO that carried out a population study there.

"The rescue efforts are underway, we cannot talk of the number of those injured at the moment," Nairobi Police chief Benson Kibue told AFP.