World Vision has deployed rapid response teams to the Solomon Islands after a powerful earthquake triggered a tsunami killing at least nine people.
The Christian development agency said the homes of up to 700 families had been damaged or destroyed.
In Lata, the main town on Santa Cruz island, there is no power or running water.
In two coastal communties in the north-east of Lata, World Vision staff report that 90 per cent of homes have been damaged. Schools and churches have also been destroyed or badly damaged.
"Access to clean water and sanitation will be critical in the coming days," said Jeremiah Tabua, Emergency Response Coordinator for World Vision in the Solomon Islands.
"The tsunami destroyed clean water sources, ruined food gardens and demolished houses.
"There are also some fears of another tsunami due to the ongoing aftershocks of the earthquakes."
World Vision has prepositioned aid in the capital, Honiara, to be shipped to Lata on Thursday evening. The items will be distributed among 3,500 people.
"Debris and water on the runway left behind by the tsunami at the airport in Lata have prevented aid from reaching the people most in need. So we hope to reach some of the most remote communities by boat," said Andrew Catford, World Vision's Country Programme Director in the Solomon Islands.
"The supplies we're bringing include tarpaulins, blankets, water containers, hygiene supplies, baby kits, emergency kits, kitchens sets and mosquito nets."
The organisation is also providing boats and fuel to government assessment teams as they try to access the remote outer islands to determine the impact of the earthquake and tsunami.
Mr Catford added: "It's a process that could take some time given the number of remote communities in low-lying atolls."