"From our countrywide assessment, we know of 23 people dead at the coast, the refugee camps and other areas of north eastern province," Linet Atieno, an information officer with the Kenyan Red Cross Society, told Reuters.

Government officials in the coastal province said thousands were fleeing the rising water for shelter in the hills of Kwale district.

Roads have been blocked and many students sitting national high school exams have been cut off from schools and examinations centres.

"The number of people displaced (are) 80,000 and thousands more are affected and at high risk countrywide," the Kenya Red Cross Society said in a statement.

"Flooding is also expected to occur in the traditional flood-prone areas of western Kenya, with rivers threatening to break their banks."

The national Red Cross appealed for 500 million shillings (US$7 million) to assist the 300,000 people it said were affected.

Officials in the northeastern region said aid would be delivered by plane because roads were impassable.

"Military aircraft will arrive soon to distribute relief food," provincial commissioner Joseph Kimeu Maingi said.

The UN refugee agency UNHCR said the flash floods have destroyed hundreds of homes and killed a pregnant woman and a child in the Dadaab refugee camps in northeastern Kenya. Thousands of Somali refugees fleeing tension in their country have been pouring into the Dadaab camps in recent months.

Heavy rains have also been pounding the Horn of Africa beyond Kenya, bringing misery to parts of Somalia, Ethiopia, Sudan and Eritrea. Thousands have been driven from their homes in southern Somalia.