The woman Obama refers to as "Granny Sarah" told The Times of London Hussein Onyango Obama, the president-elect's paternal grandfather, was arrested in 1949 and jailed for two years in a high-security prison.
"The African warders were instructed by the white soldiers to whip him every morning and evening until he confessed," said Sarah Onyango, his third wife.
In a story published Wednesday, the London newspaper said the beatings and abuse made Barack Obama's grandfather loathe the British.
He became involved in the Kenyan independence movement while working as a cook for a British army officer after World War II.
Although he was from a different tribe, Obama's grandfather sympathized with the organization leading the movement that would eventually stage the Mau Mau rebellion, says The Times.