A powerful cyclone made landfall in northern Mozambique on Thursday evening, barely a month after a super-storm slammed into the country's center, leaving hundreds dead and causing devastation.
Cyclone Kenneth hit the north coast of Mozambique in Cabo Delgado province after swiping the Comoros.
The U.N. warned of flash flooding and landslides.
Some parts of the city are in darkness, and strong winds have felled trees and destroyed boats.
"Cyclone Kenneth is currently making landfall on the north coast of Mozambique," the U.N. World Food Programme (WFP) said in a statement.
"The Cyclone is expected to bring heavy rains in the area for several days, with over 600 millimeters rainfall expected."
That volume of rain would be nearly double the 10-days accumulated rainfall that caused flooding in Beira during Cyclone Idai.
Forecasters at Meteo-France warned that Kenneth could trigger waves off Mozambique's northeastern shore as much as five meters (16 feet) higher than usual.
"I was quite preoccupied by the sea because they announced six-meter waves ... the wind was very strong, and I've never seen anything like it in my 15 years in Pemba," a Portuguese owner of a lodge on Wimby beach, Anabela Moreira, told French Press Agency (AFP).
Another local, Jonas Wazir told AFP that he "noticed that some precarious houses had fallen down."
A reporter for the state daily newspaper, Noticias, said the electricity supply in the city was down and strong winds had been gusting since this afternoon.
The Red Cross warned it was "especially concerned" about the storm's impact, as many communities in Mozambique are still recovering from a cyclone that hit on the night of March 14-15.
The most powerful storm to strike the region in decades, Cyclone Idai cut a path of destruction through Mozambique, Malawi and Zimbabwe. It left more than a thousand dead and causing damage estimated at around $2 billion (1.8 billion euros).
Kenneth passed by the Indian Ocean archipelago nation of Comoros on Thursday, battering it with high winds and heavy rains, the country's Meteorological Office wrote on Facebook.
"We must stay alert, avoid touching fallen power cables, wait for permission before driving and keep children at home," it said.
An AFP team in the Comoran capital Moroni saw shacks destroyed by the rain and wind, and high seas as a result of the cyclone.
"I have three children, one is small, just one month and 10 days (old). We were here until 11 pm last night when things deteriorated," local resident Abdillah Alaoui told AFP.
"It was our neighbors who evacuated us."
Tanzanian authorities ordered schools and businesses shut in some southern districts on Thursday and urged people to brace for extreme winds and rain.
The Tanzanian provinces of Mtwara, Lindi and Ruvuma were at highest risk and could experience strong winds and downpours from the middle of the Thursday, the country's meteorological agency said.
Residents in Mtwara were already leaving the coastal enclave with their families, some on foot, for emergency shelters, witnesses told AFP by phone.
Gelasius Byakanwa, the governor of Mtwara, ordered schools closed in his province and asked "students to stay home and employees not to go to their offices".
However, he called on medical staff, police and utility workers to remain on duty.
"This storm will hit the north and we are expecting that heavy rain will provoke flash floods and landslides impacting the northeastern provinces of Cabo Delgado and Nampula," the WFP said in a statement earlier.
"WFP is working under government coordination and with other humanitarians on an emergency preparedness plan."