At least 16 people have died in flooding in the Solomon Islands, while 40 others are missing and up to 49,000 have become homeless, an aid official has said.
The disaster has raised fears that a lack of sanitation and fresh water will lead to an outbreak of dengue fever in the Pacific Island nation.
"It's grown a lot worse," Save the Children's emergencies manager Graham Kenna said on Saturday as reports filtered in of the havoc outside the capital Honiara, according to AFP news agency.
"The last report we had was there are 16 in the mortuary and at least 40 still missing, most of them children and it's very unlikely they'll be found alive," Kenna said.
"There are 49,000 who have lost their homes and are seeking temporary shelter."
Kenna said aid agencies urgently needed tents and tarpaulins but they could not be flown in while the airport remained shut after two houses floated onto the runway.
The city's main river, the Matanikau, burst its banks in a torrential tropical storm late on Thursday, sweeping away riverside communities, bringing down bridges and inundating the downtown area.
My staff has witnessed a child being swept away by the floodwaters, they are devastated by what they have witnessed
The Red Cross secretary general in the Solomons, Joanne Zoleveke, described the devastation as "a tragedy none of us saw coming".
"We were watching the river but never expected it to rise so fast. It took us by surprise. That is why there are deaths," Zoleveke said.
World Vision's Emergency Response Manager in the Solomon Islands, Lawrence Hillary, told Fairfax News the organisation was particularly concerned about the welfare of children.
"My staff has witnessed a child being swept away by the floodwaters. They are devastated by what they have witnessed"
Aid workers feared outbreaks of disease and were waiting for Honiara's Henderson International Airport to reopen so emergency relief supplies could be flown in.
"Thousands of people are living in schools and other cramped conditions with poor sanitation and relying on rainwater for drinking," Kenna said.
"We expect an outbreak of dengue fever in two weeks," Kenna said.
The loss of the bridges prevented officials seeing the scale of destruction caused by landslides and floods in outlying areas although a helicopter had been able to make reconnaissance flights from Honiara.
As Solomon Islanders battled the floodwaters they were also shaken by a strong 6.0 magnitude earthquake late on Friday, but there were no reports of any damage.