AVA- The official death toll stands at 84 following flooding and high winds, which have destroyed homes and ripped roofs from concrete buildings.
The cyclone has killed at least 160 people across southern Africa.
On a visit to Beira, President Nyusi said that its impact had been devastating, adding that he had seen bodies floating in the floodwater.
Earlier, the International Federation of Red Cross and Red Crescent Society (IFRC) described it as "massive and horrifying".
People have had to be rescued from trees, head of the IFRC assessment team, Jamie LeSeur, told media.
In neighbouring Zimbabwe, more than 80 people have died in the east and south, information ministry head Nick Mangwana told Reuters news agency.
This includes two pupils from the St Charles Lwanga boarding school in the district of Chimanimani, who died after their dormitory was hit when rocks swept down a mountain.
Malawi has also been badly hit. The flooding there, caused by the rains before the cyclone made landfall, led to at least 122 deaths, Reliefweb reports.
How bad is the damage in Beira?
At least 84 people have died in Mozambique, mostly around Beira, the country's fourth largest city with a population of about 500,000, the authorities there say.
More than 1,500 people have been injured by falling trees and debris from buildings including zinc roofing, the BBC's Jose Tembe in the capital, Maputo, quotes officials as saying.
"Almost everything has been affected by the calamity," Alberto Mondlane, the governor of Sofala province, which includes Beira, said on Sunday.
"We have people currently suffering, some on top of trees and are badly in need of help."
Monday 18 March 2019 21:36