"The Sudanese government may be systematically rounding up suspected rebel or opposition supporters in Khartoum," said African Director for Human Rights Watch Georgette Gagnon. "Given Khartoum's record of abuse, there is grave cause for concern about the fate of those detained."
Sudanese officials arrested at least 100 rebel supporters since the Darfur rebel group Justice and Equality Movement Saturday raided the city of Omdurman, Sudan's largest city.
Residents of Omdurman told Human Rights Watch fighting continued Monday in the market areas. At least 60 civilians died in the conflict.
"Details of the clashes are unclear but the continuing fighting in the markets means civilians are at terrible risk," said Gagnon.