More cases of cholera have been registered in the Yemeni capital Sanaa, a World Health Organization (WHO) official said on Tuesday.

The United Nations first reported the cholera outbreak on Friday.

"The number of cases has increased from five to 11 people," WHO official Omar Saleh told a news conference in Sanaa.

Medics were working to curb the epidemic, which has yet to claim any deaths or spread beyond the capital, he said.

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Thousands of families fleeing Yemen's war are living in camps outside Sanaa, where conditions could lead to the spread of cholera, including through contaminated food or water.

Much of the country's infrastructure, including schools and hospitals, has been destroyed by the 18-month old conflict between a Saudi Arabia-led coalition and the Iran-aligned Houthi group which controls much of northern Yemen, including Sanaa.

Saleh said that more than half of Yemen's health centers had ceased to operate since the start of the war after not receiving funds from the health ministry.

The conflict has killed more than 10,000 people and displaced millions, the United Nations estimates.