Thousands of Somalis who fled famine, drought and conflict now face the misery of heavy rains and flooding in the region, the UN refugee agency said on Friday.

"Thousands of displaced Somalis have been affected by heavy rains and flooding in parts of Somalia, Kenya and Ethiopia," High Commissioner for Refugees spokesman Andrej Mahecic told journalists.

In the Somali capital Mogadishu shelters for nearly 2,800 residents of the camp at Sigale have been destroyed, the UNHCR said, while nearly 5,000 people have been flooded out in the vast refugee camp of Dadaab in eastern Kenya.

Latrines have also been destroyed, causing a worrying increase in the number of cases of diarrhoea and a general worsening of the health of the 450,000 residents of Dadaab.

The UNHCR said however that an increase in tensions on the Somalia-Kenya border, where Kenyan forces have mounted an incursion against Shebab rebels, had sharply reduced the flow of refugees making for Dadaab.

An estimated 330,000 Somalis have fled their lawless country since January for neighbouring states including Kenya, Ethiopia, Yemen and Djibouti.