Emergency food stocks are running low in Honiara as the Red Cross struggles to feed the thousands of people left homeless by last week's devastating flash floods.
Australia and New Zealand were leading international relief efforts, preparing flights to take humanitarian supplies, emergency workers and equipment to the Solomons, three days after flash floods tore through the capital.
"There are now 21 confirmed deaths and significant numbers of displaced persons in evacuation centres across Honiara," New Zealand Foreign Minister Murray McCully said.
"We will continue to work with the authorities in Solomon Islands and further support will be considered as the full extent of the damage becomes clear."
Desperate search for survivors
Tearful residents and aid workers continued to scour debris for bodies on Sunday.
Although the chances of finding more survivors appeared remote, officials said they could not give up hope.
"We had one father who had been separated from his wife and children for two days and we were able to track the family down," Red Cross aid worker Cherise Chadwick told AFP.
The death toll was put at 21, with aid agencies saying up to 40 people remained unaccounted for and about 49,000 had been displaced.
"Some people who went into the river will probably not be found as they would have been swept out to sea," Chadwick said, adding that the Red Cross had played a leading role rescuing people after the Matanikau River burst its banks.
"The Red Cross office is by the river and we were the first line of response, actually pulling people from the river, saving lives that day."
Floodwaters and landslides swept away riverside communities as Honiara was pounded by a torrential tropical storm on Thursday, causing severe infrastructure damage to fresh water supplies, sewerage systems and electricity.
Following a meeting with aid agencies, the UN Office for the Coordination of Humanitarian Affairs listed their priorities as emergency shelter, food, health, protection of vulnerable people, psychosocial support and water, sanitation and hygiene.
The international airport was reopened Sunday, after hasty work to remove two houses and other debris that were washed onto the runway, paving the way for the arrival of flights carrying urgently needed relief supplies.