Death toll from Kenya's flash floods ravaging several parts of Kenya have so far killed at least 50 people and displaced thousands of others in the east African nation, a humanitarian agency said on Saturday.

The Kenya Red Cross Society (KRCS) spokesperson Nelly Muluka said four people were swept away by flood waters near Rongai on Friday night.

The relief agency said the number of flash flood fatalities will still continue to rise due to heavy rains that have led to flash floods in several parts of the country.

"At least 50 people have lost their lives as a result of the flooding since March. Four people were swept away by flood waters near Rongai on the night of May 4. Their bodies were found on top of the Rimpa bridge in Rongai on Saturday morning," Muluka said.

According to Muluka, on another case on the same night, one man drowned in Acacia River and two others in River Kwekwe in Kiserian, about 40 kilometers south of Nairobi.

"The latter were in a car and their retrieval is underway. In Ruai, a family has been marooned since last night following heavy rains that caused floods near Clayworks next to Mebri, Thika," she said.

The relief agency said efforts to rescue them have been hampered by rising water levels of up to about 1.5 meters. In the same area, 10 households were affected with water up to the knee level flowing into their houses and destroying property.

"The main challenge to rescue efforts is accessibility and high water levels. Meanwhile major flooding has been reported in Athi River at Kwanzomo and Mangeli informal settlements and property worth lots of money destroyed," she said.

The floods are the result of torrential rains that have eased Kenya's long drought but are making life miserable for people who live near rivers and in flood-prone areas.

Muluka said the most affected regions are in Western Kenya where heavy rains have washed away bridges and rendered many roads impassable, making difficult efforts to reach thousands of people made homeless by the flooding.

On Friday, she said, two middle aged people drowned in River Seia at Lodundokwe, Samburu East, adding that KRCS and the locals' rescue efforts to retrieve the bodies were hampered by heavy rains and so, the bodies are still missing.

The heavy rains that have been pounding several parts of the country since March are now bearing toll on the city of Nairobi.

In the last three weeks, heavy rains in Nairobi have resulted into flash floods rendering several roads impassable with trees falling across some roads, vehicles breaking down and others being swept away in flood waters and traffic jams.

Some of the hardest hit areas are parts of major city roads linking the central business district with a number of residential estates.

On Thursday evening, heavy rains had effects in several parts of Nairobi including the police staff quarters, several houses were marooned, along Mombasa road, a big tree fell and blocked the road, causing heavy traffic jams as major roads were flooded and rendered impassable.

The humanitarian agency was currently undertaking an assessment through its branches countrywide to establish the magnitude of the problem and identify the most vulnerable of those affected and areas which we have not reached because of logistical challenges.

Relief agencies and Kenyan officials say the number of casualties may rise as the rains are expected to continue for days or weeks to come.

The Red Cross said the displaced and those affected by the floods urgently require relief aid such as food, mosquito nets, tents, blankets, cooking utensils and medicine.

Peter Ambenje, head of forecasting at the Met Department said that most parts of the east African nation will continue to receive heavy rainfall that leads to floods.

These areas include Western, Central highlands and the capital Nairobi. The areas are among those that have suffered greatly because of the ongoing heavy rains.

Statistics of victims of floods in these areas continue to increase as rains pound heavily the regions.

Due to the heavy rains being experienced in Mount Kenya Region, Muluka said the agency has issued an alert to families living in the low lands along the Tana River especially the farmers who practice irrigation along the river in Garissa and Tana Delta to take precaution and move to higher grounds.

"This is because both Kindaruma and Masinga dams are full to capacity and KenGen may be forced to discharge the water. The spillage is likely to result into flash floods as the water levels of the Tana River rise," she said.

"When the water is released, it will take 72 hours to be within the areas that are likely to be affected."