The United Nations World Health Organization (WHO) on Friday expressed concerns over increased number of cholera cases in southern Somalia, particularly in militant controlled town of Kismayo.

"Out of the 65 patients treated so far in the same health facility, 40 suffered severe dehydration and needed immediate hospitalization. The majority of the cases are children under the age of eight," Pieter Desloovere, spokesman for WHO Somalia said in a statement.

Cholera caused by drinking water or eating food contaminated by the bacterium Vibrio cholerae is endemic in Somalia, and cases are reported throughout the year, WHO said.

Untreated, the acute diarrhoeal disease can kill within hours, Dr. Marthe Everard, WHO's Somalia Representative, warned.

WHO said since the beginning of the year, Kismayo General Hospital reported a total of 639 suspected cholera cases.

"However since May 2012, the health facility reported an average of 40 suspected cholera cases on a weekly basis," The UN health agency said.

WHO said it will be responding to the sudden increase of suspected cholera cases by sending five diarrhea disease kits to the affected areas. One diarrhea disease kit can treat 400 moderate and 100 severe diarrhea cases.

"Adequate case management supplies have been prepositioned in strategic locations, particularly the riverine areas such as Lower and Middle Jubba, Lower and Middle Shabelle, Hiraan and Gedo regions," said Desloovere.

The UN health agency stated, however, that various challenges such as limited access and the recent fighting in the area make it difficult to fully respond.

The last cholera outbreak in Somalia occurred in November 2011 and was declared under control at the end of December 2011.