At least 31 people have been killed and dozens are missing as tropical cyclone Idai hit eastern parts of Zimbabwe after lashing neighbouring Mozambique, the government said on Saturday.

Most of the deaths were in Chimanimani East, Zimbabwe's information ministry announced on Twitter.

Two of the victims were students who died after a landslide sent a boulder crashing into their dormitory, collapsing the wall of the dining room and trapping 50 of them, the country's Department of Civil Protection (DCP) said in a statement.

The boarding school has been shut and the army, which is leading rescue operations, is moving in to take the nearly 200 students to safety.

“So far a total of 71 people are reported missing,” said the DCP.

Others who had fled their homes were stranded on top of a mountain waiting to be rescued, as strong winds hampered helicopter flights, the ministry said.

The storm damaged many houses and washed away bridges in the eastern Manicaland province which borders Mozambique. Thousands of people have been affected by power cuts and flooding, a lawmaker told AFP.

Earlier Saturday, Joshua Sacco, an MP in Chimanimani district, told AFP that more than 100 people were missing. Around 100 houses had been swept away in Ngangu township in Chimanimani town, he said.

The opposition Movement for Democratic Change called for immediate help for the storm-hit east, warning that a “serious humanitarian crisis” was unfolding there.

“We need state intervention on a massive scale to avoid biblical disaster,” MDC spokesman Jacob Mafume wrote on Twitter.

President Emmerson Mnangagwa, who is currently on a visit to Abu Dhabi, has declared a state of disaster in the affected areas.

'Dire situation'

Tropical cyclone Idai battered central Mozambique on Friday killing at least 21 people and cutting off more than half a million people in the port city of Beira.

Even before the cyclone made landfall on Friday, heavy rains earlier in the week had already claimed 66 lives and forced 17,000 people from their homes in Mozambique, local officials said.

They also affected neighbouring Malawi, where 56 people died, the government said.

As the cyclone hit, Mozambique's President Filipe Nyusi appealed for emergency assistance for the victims before leaving for eSwatini.

“We have compatriots suffering without hope and we have to restore hope,” he said on Friday as he set off on a three-day state visit to the kingdom previously known as Swaziland.

As the cyclone approached, the Red Cross sent out more than 200 volunteers to areas most likely to be affected.

“The situation is dire but we don't know the exact particulars,” said Jamie LeSueur, the Red Cross's roving emergency operations manager for Africa.

He was making the 1,200-kilometre (745-mile) trip from Maputo to Beira by road after flights were cancelled and the airport closed.

It would require “the full force of the humanitarian community behind the government of Mozambique to respond to rapidly”, he told AFP.

South Africa rations electricity

Beira's international airport was closed after the cyclone made landfall, damaging the air traffic control tower, the navigation systems and the runways.

“Some runway lights were damaged, the navigation system is damaged, the control tower antennas and the control tower itself are all damaged,” an official at the National Institute of Disaster Management (NIDM) told AFP on Friday.

“The runway is full of obstacles and parked aircraft are damaged.”

The storm also affected power supplies to neighbouring South Africa which imports electricity from Mozambique to supplement its own production.

South Africa's power utility company Eskom on Saturday introduced electricity rationing “due to the loss of additional capacity, which includes a reduction in imports from Mozambique,” it said in a statement.