WHO spokesman Pieter Desloover says Mogadishu, Afgoye and Baidoa have been hit hardest by the disease. Banadir hospital in Mogadishu alone reported 85 deaths.
He says the cholera outbreak was declared in April.
Some 2,403 acute watery diarrhea and cholera cases were reported this year. Most were children under 5 years old.
The agency warned hat waterborne diseases could spread during the rainy season. Somalia is currently suffering from a drought and there are few sources of clean water.
The arid Horn of Africa nation has not had a functioning government for 20 years and has few working health facilities.