A cyclone struck northern Mozambique leaving at least eight people dead on Friday, the national institute for risk management said.

Among the victims was a child crushed in the collapse of a house in Monapo, the institute said, raising the toll to eight.

President Filipe Nyusi had earlier announced on a visit to South Africa that seven people were dead.

Cyclone Gombe hit Nampula province overnight Thursday-Friday packing powerful winds -- forecast to reach 160 kilometres per hour (100 mph) -- and torrents of rain, causing serious damage to homes, the weather service said.

"Preliminary information indicates that there are seven deaths, two in the city of Nampula as a result of collapsed houses and five in Angonche," 170 kilometres to the southeast on the Indian Ocean, the president said earlier from Pretoria.

"There are communication problems with the most affected districts in Nampula," he added, warning of a flood risk from the Licungo River.

"There are many fallen trees and electricity poles are on the ground and can cause damage," Nyusi said.

The cyclone weakened to a tropical storm later Friday but heavy rain continued to fall including over neighbouring provinces.

Electricity and water were cut in Nampula where mobile phone service was disrupted, reports said.

Flights to the province had been halted before the cyclone struck, the national carrier LAM said.

Aid groups were preparing to deploy in the region after Tropical Storm Ana in January left a trail of destruction and killed about 100 people across Madagascar, Mozambique, Malawi and Zimbabwe.