Kenya and Tanzania were on alert on Saturday for a cyclone heading towards their Indian Ocean coastlines, threatening to pile on more misery after deadly floods that have ravaged the region.

About 400 people have lost their lives in East Africa and tens of thousands have been uprooted from their homes in recent weeks as torrential rains triggered flooding and landslides engulfed houses, roads and bridges.

Kenyan President William Ruto on Friday described the weather outlook as "dire" and postponed the reopening of schools indefinitely as the nation braced for its first-ever cyclone.

Tropical Cyclone Hidaya is projected to make landfall at the weekend on the Kenyan and Tanzanian coasts.

Ruto said the storm "is predicted to cause torrential rain, strong winds and powerful and dangerous waves".

Around 210 people have died in Kenya from flood-related incidents and nearly 100 are missing while 165,000 have been forced to flee their homes, according to government data.

"No corner of our country has been spared from this havoc," Ruto said. "Sadly, we have not seen the last of this perilous period."

The Kenya Met Department said Cyclone Hidaya was expected to hit coastal areas with powerful winds surpassing 40 knots and ocean waves over two metres (more than six feet) high.

On Thursday, the interior ministry had ordered anyone living close to major rivers or dams to leave the area within 24 hours or face "mandatory evacuation for their safety".

It warned that 178 dams and water reservoirs were full or almost full and may spill over, posing a risk to people in their vicinity.

Opposition politicians and lobby groups have accused the government of being unprepared and slow to respond despite weather warnings.

- 'Maximum precautions' -

Cyclone Hidaya will peak at gusts of 165 kilometres (100 miles) per hour when it makes landfall in Tanzania on Saturday, according to the Climate Prediction and Applications Centre for East African trade bloc IGAD.

Cyclone season in the southwest Indian Ocean normally lasts from November to April, and there are around a dozen storms each year.

The Tanzanian Meteorological Authority said in a statement posted on X on Saturday that the cyclone was about 125 kilometres from the main city of Dar es Salaam late Friday, causing strong winds and heavy rains in several coastal areas.

It has advised people living in the risk-prone areas and those involved in marine activities to take "maximum precautions".

At least 155 people have already been killed in Tanzania by floods and landslides that have destroyed crops and swallowed homes.

East Africa is highly vulnerable to climate change and the rains this year have been amplified by the El Nino weather pattern -- a naturally occurring climate phenomenon typically associated with increased heat worldwide that leads to drought in some parts of the world and heavy downpours elsewhere.

The heavier than usual rains have also claimed at least 29 lives in Burundi and displaced tens of thousands since September, the United Nations said.

UN refugee agency UNCHR said it was "particularly concerned" about thousands of refugees who had been displaced in Burundi, Kenya, Somalia and Tanzania.

"(They are) being forced to escape once again for their lives after their homes were washed away," UNHCR spokesperson Olga Sarrado Mur said on Friday.

Late last year, more than 300 people died in rains and floods in Ethiopia, Kenya and Somalia, just as the region was trying to recover from its worst drought in four decades.