Cyclone Kenneth has made landfall in northern Mozambique, a country still recovering from another huge storm.
The cyclone has weakened in the past few hours but is forecast to cause flooding and bring storm surges of up to 5m (16ft).
Mozambique’s National Institute of Disaster Management (INGC) said 30,000 people had been evacuated from areas likely to be hit.
Last month, Cyclone Idai caused hundreds of deaths in the region.
More than 900 people died when the storm brought devastation to Mozambique, Malawi and Zimbabwe.
At least three million people were left in need of humanitarian assistance.
The latest system is expected to hit further north than Idai, forecaster say.
What is the latest?
Kenneth made landfall with wind speeds equivalent to a Category 4 hurricane on the north coast of Mozambique on Thursday evening.
It arrived in the northern city of Pemba with maximum sustained winds of 220km/h (136mph), according to the Joint Typhoon Warning Center.
A “compulsory evacuation” of families is under way and will continue “until we have all people in secure ground”, INGC spokesman Paulo Tomas said.
More than 680,000 people are said to be at risk from the cyclone, Mozambican officials said on Wednesday.
Forecasters warn it is likely to be slow-moving, meaning heavy rain is expected to fall on the area for several days.
Flights have already been cancelled and schools closed as Mozambique braces for the storm to hit.
Residents in the southern Tanzanian town of Mtwara were told to seek higher ground and shelter, but that warning has been stood down.
The path of the cyclone has shifted south, meaning a major catastrophe is no longer expected, regional commissioner Gelasius Byakanwa told reporters.
“That has informed [our decision] to allow the residents to go back home and carry on with their daily activities.” he said.
Kenneth’s violent winds and rains hit the island nation of Comoros overnight. Authorities there say the storm killed at least three people as it swept through.
The country’s two main islands saw power outages and trees downed in high winds, Reuters news agency reports.
The International Federation of Red Cross and Red Crescent Societies shared images of the damage on social media.
In a tweet, the group confirmed it had volunteers on the ground assisting communities.
Late on Wednesday, the head of the UN Office for Disaster Risk Reduction said she feared the region faced “another humanitarian catastrophe”.
Mami Mizutori shared an image which showed the large storm system on Twitter, warning it was already comparable in intensity to Cyclone Idai.
There is no previous record of hurricane-force systems ever hitting the region so far north before, BBC Weather reports.
The storm is expected bring 1m of rain to some areas of Mozambique.
Despite Zimbabwe being further inland, officials there say they are still putting their disaster management agencies on alert.
“Drawing lessons from Cyclone Idai we cannot take chances any more,” said Department of Civil Protection Director Nathan Nkomo.