More than 350 people have been confirmed dead and hundreds more are missing after the cyclone that unleashed devastating floods in Mozambique, Zimbabwe and Malawi.

Aid workers rushed to rescue victims clinging to trees and crammed on rooftops on Tuesday amid fears that many thousands of people are at risk.

In Mozambique, the rapidly rising floodwaters created “an inland ocean,” endangering tens of thousands of families, aid workers said as they scrambled to rescue survivors and airdrop, food, water and blankets to survivors of Cyclone Idai.

Zimbabwe Cyclone
A family dig for their son who got buried in the mud when Cyclone Idai struck (Tsvangirayi Mukwazhi/AP)

“This is the worst humanitarian crisis in Mozambique’s recent history,” said Jamie LeSueur, head of response efforts for the International Federation of Red Cross and Red Crescent Societies.

The United Nations allocated 20 million (£15m) from its emergency response fund to ramp up the humanitarian response in Mozambique, Zimbabwe and Malawi.

The European Union and Britain have also pledged aid, and the US Embassy in Zimbabwe said America was “mobilising to provide support” to partners in the three affected countries.

Mozambique’s President Filipe Nyusi said that more than 200 people had been confirmed dead in his country. Earlier he said the death toll could reach 1,000.

At least 400,000 people have been left homeless.

Zimbabwe Mozambique Cyclone
A man stands on the edge of a collapsed bridge (Tsvangirayi Mukwazhi/AP)

In Zimbabwe’s eastern mountain areas bordering Mozambique, residents struggled to cope with the disaster.

“There was a house there, it was buried and the owners may have been buried with it. They are missing,” said Zacharia Chinyai of the Zimbabwean border town of Chimanimani, who lost 12 relatives in the disaster.

The cyclone took residents by surprise, Mr Chinyai said.

“We heard news on the radio” about the flooding in neighbouring Mozambique, he said. “But we never thought we could also be victims… No-one told us it was going to be this devastating.”

Chipo Dhliwayo lost her daughters, four-year-old Anita and eight-year-old Amanda.

“I wasn’t able to save anything except this baby,” she said of her lone surviving child, a six-month-old son, who suffered an eye injury and scars to his face.

The family was sleeping when their house collapsed, the 30-year-old said.

“Trees, rocks and mud were raining on us. I grabbed my son, my husband took Anita and we ran to a hut, but that also collapsed. Anita died there,” she said.

Amanda was trapped in the rubble of their house and her body was not found until the next day.

“I knew she was already dead. I cried the whole night,” Ms Dhliwayo said. “I lost so much that I wish I had just died.”

The cyclone created southern Africa’s most destructive flooding in 20 years, said emergency workers. Heavy rains were expected to continue through Thursday.

Mozambique’s Pungue and Buzi rivers overflowed, creating “inland oceans extending for miles and miles in all directions,” said Herve Verhoosel of the World Food Programme (WFP).

“This is a major humanitarian emergency that is getting bigger by the hour,” Mr Verhoosel said.

He said people were “crammed on rooftops and elevated patches of land.”

“People visible from the air may be the lucky ones and the top priority now is to rescue as many as possible,” he said.

“The full horror, the full impact is only going to emerge over coming days,” Red Cross spokesman Matthew Cochrane told reporters in Geneva.

In Zimbabwe the death toll was 98 but expected to rise, a local government minister, July Moyo, said.

He said bodies of Zimbabweans had been reported floating all the way into Mozambique. “Some of the peasants in Mozambique were calling some of our people to say: ‘We see bodies, we believe those bodies are coming from Zimbabwe’,” Mr Moyo said.