Relief workers are trying to reach Vanuatu's remote outer islands that were smashed by a huge cyclone over the weekend.

The UN says 24 people are confirmed dead and 3,300 are displaced by the storm that tore through the South Pacific archipelago on Saturday.

The UN Disaster Assessment and Co-ordination team in the capital, Port Vila, said 37 evacuation centres had been set up, but communication with outer islands was still down.

President Baldwin Lonsdale said the storm had "wiped out" all development of recent years. He called again for international aid.