Some 15,000 people still need to be rescued from the devastation caused by Cyclone Idai, Mozambique officials say.

The cyclone victims there are stranded by catastrophic flooding and are clinging to roofs or stuck in trees, charities say.

In the port city of Beira, aid workers say there is only two to three days of clean water left.

Some 300 people are confirmed dead in Mozambique and Zimbabwe, but the toll is expected to rise.

'Destruction and a lot of water'

With shortages of food and clean drinking water the threat of disease is growing, medical agencies warn.

The powerful cyclone swept in to Beira last Thursday, with winds of more than 177km/h (106 mph). It left a trail of devastation as it moved inland across Zimbabwe and Malawi.

"The first thing you see when you arrive is destruction and a lot of water," said Get Verdonck, an emergency co-ordinator with the medical charity Médecins Sans Frontières (MSF).

"People are using well water with no chlorination, and that water is unlikely to be clean... pneumonia and other respiratory diseases are going to be a problem," he told Reuters from Beira.

Aid groups said Mozambique had borne the brunt of flooding from rivers that flow downstream from neighbouring countries. A total of 217 people are confirmed dead in the country but many areas have still not been reached.

Caroline Haga, an official with the International Federation of Red Cross and Red Crescent Societies, said the worst-hit areas were close to the Buzi river west of Beira.

She said rescue teams were dropping high-energy biscuits, water purification tablets and other supplies to people surrounded by water and mud.

"We have thousands of people... in roofs and trees waiting for rescue," Ms Haga told AFP news agency.

"We are running out of time. People have been waiting for rescue for more than three days now. We can't pick up all the people so our priority are children, pregnant women, injured people."

Deborah Nguyen, of the World Food Programme (WFP), said the priorities were reaching people trapped in the flooded areas and then organising temporary shelter for those rescued.

"Relief operations are progressing, but there is still a lot of work," she told AFP.

Mozambique President Felipe Nyusi has said more than 100,000 people are at risk.

'I didn't have any way of leaving'

Wilker de Assis de Sousa Dias, a survivor of Cyclone Idai, speaking to BBC Focus on Africa

The winds started on Wednesday, but only around 60km/h. On Thursday, at around 14:00 it started getting at worse, and at around 19:00, the show really started, if I can say that. The cyclone was already starting to cause damage, picking up everything in its path. It was just destroying everything.

In the parts of the city which are near the sea, there is almost nothing left. My house has two floors, and there's basically nothing there now. The roof has given way, and water is coming in from every corner. I was in my house during the storm. I actually didn't have any way of leaving, even if I'd wanted to. All of the roads near the sea, where my house is, were flooded. The wind was so strong it was picking up stones and hurling them around. I saw stones flying, zinc sheets flying, even pieces of cars. The debris smashed all of the windows in my house.

I was able to walk around some of the affected areas shortly after the storm. I would say that 75% of the city is totally destroyed. We're still waiting for help. We need food, certainly, and we urgently need construction materials.

What has happened elsewhere?

In Zimbabwe, at least 98 people have died and 217 people are missing in the east and south, the government said.

In Malawi, the UN says more than 80,000 people have been displaced by the cyclone.