The World Health Organization (WHO) says nearly 200 children in Somalia have been paralyzed with polio since the disease re-emerged in the African nation last year.
The U.N. agency said the disease has recently spread to two new regions of the country, Lower Juba in the south and Mudug region in the northeast.
It said it will launch a nationwide vaccination campaign on Sunday to try to reach 1.4 million Somali children.
Despite the new outbreaks of polio, the WHO said it appears to be on the decline in the capital, Mogadishu, which was at the center of the current outbreak.
U.N. health officials believe the disease was spread from northern Nigeria, where Muslim leaders suspended polio immunizations in 2003 for nearly a year, claiming the vaccine caused sterility.
The Nigerian polio strain was blamed for sparking epidemics in more than a dozen countries.
Polio attacks the nervous system in young children causing paralysis, muscular atrophy and sometimes death.
Some information for this report was provided by Reuters.