Britain has pledged a further £12 million in aid to help survivors amid the devastation caused by Cyclone Idai across parts of Africa.
The support package includes food, water and shelter and brings the Government’s total donation in the aftermath of the cyclone to £18 million.
Authorities in Mozambique fear the death toll could be more than 1,000, while tens of thousands of people were said to have lost their homes there, as well as in nearby Malawi and Zimbabwe.
The United Nations (UN) described victims trapped on rooftops and clinging to trees awaiting rescue, and said roads, bridges and crops have been washed away.
More than 200 have been confirmed dead in Mozambique, more than 100 in Zimbabwe, and around 60 in Malawi, the UN said, adding that hundreds were injured and many more were unaccounted for.
In response to the destruction, Britain announced on Wednesday a further £12 million in aid, adding to £6 million pledged on Monday.
Major broadcasters will air appeals on Thursday in support of fundraising by the Disasters Emergency Committee (DEC) aid agencies coalition.
International Development Secretary Penny Mordaunt said it was “one of the biggest natural disasters to ever hit the region”.
The UN’s Central Emergency Response Fund (CERF) allocated 20 million dollars on Wednesday to deal with the disaster.
The British Red Cross has made an urgent appeal for donations to deal with the “severe humanitarian emergency”, while a charity worker with Concern said there was a real risk of the spread of water-borne diseases.
It is feared the situation could become even more challenging, with heavy rain predicted in the coming days, British Red Cross said.
Ben Webster, head of emergencies at the charity, said: “Cyclone Idai has wreaked devastation across a vast area. People living in the path of the storm have seen family members lost in the floods, they’ve seen their homes and livelihoods washed away. This is a severe humanitarian emergency.
“Right now the primary focus is to save lives, but the after-effects of this crisis will be felt for some time to come.”
He said the developing picture made “clear this disaster will require a huge international response”.
The charity has provided 2,000 tarpaulins, 3,000 mosquito nets and 3,000 blankets from its regional warehouse in Harare to the Zimbabwe Red Cross and has released some emergency funds through its community resilience programme in Zimbabwe.
Local Red Cross volunteers were helping with search and rescue operations, the distribution of aid and facilities for temporary camps.
Concern’s Yousaf Jogezai said nearly one million people were affected in Malawi alone, where nearly 600 have been injured and more than 50 people have been killed.
Many of the survivors, whose homes have been destroyed or submerged in floodwater, were now taking shelter in overcrowded schools and churches, where it was feared disease could spread.
Mr Jogezai said: “In some places they have hundreds of people. They don’t have enough facilities such as water or latrines. So it is posing a very serious risk, which may spread water-borne diseases such as cholera and diarrhoea, so that’s a big risk.”
He said crops which had been just one month from harvest have been completely destroyed, meaning basic necessities were urgently needed.
Noting that some communities had already been devastated by serious floods last year, he added: “They urgently need support from the international community and international organisations such as Concern to come forward and provide this lifesaving assistance.”
Concerns were raised earlier on Wednesday that the response to the cyclone, which hit the region last Thursday, was slower than it should have been.
Conservative former international development secretary Andrew Mitchell said the search and rescue response to the natural disaster was “much slower than in the crisis” following a previous cyclone in 2000, and said Cyclone Idai was heading towards being the “worst weather-related disaster to hit the southern hemisphere”.
DEC chief executive Saleh Saeed said delays are caused because the extent of the devastation is unknown while authorities and aid workers on the ground are “overwhelmed”.
“When the scale becomes evident, as it has become now, it’s clear that the DEC needs to activate,” he said.
Ms Mordaunt heralded the UK as “one of the first countries to respond to this disaster”.
She added: “I’ve been extremely moved by the images I’ve seen of this devastating cyclone which has caused misery for millions of people across Mozambique, Malawi and Zimbabwe. This is, undoubtedly, one of the biggest natural disasters to ever hit the region, and our thoughts remain firmly with the victims of this cyclone.
“Today’s UK aid package is a sign of the UK’s commitment to do all we can to make sure those in desperate need of humanitarian relief have access to life-saving essentials, including food, water and shelter.”
Tents and thousands of shelter kits were sent to the country on Tuesday and further help will include ensuring families have access to clean water and providing food and food vouchers to those affected.
To donate to the DEC appeal, visit www.dec.org.uk or call the 24-hour hotline on 0370 60 60 610.