A state of emergency has been declared for Vanuatu's Ambae Island as a volcano continues to spill thick heavy ash.

Thousands of residents who call the island home have been warned they may need to evacuate after up to 1cm of ash has fallen in some areas north of the island on Tuesday night.

The situation was described as 'becoming critical in some areas' and national EMT coordinator Dr Basil Leodoro told Vanuatu Daily Post they had 'received reports of houses collapsing due to the weight of the ash.'

A state of emergency has been declared for Vanuatu's Ambae Island as a volcano continues to spill heavy ash

Medical assistance teams arrived on the island on Thursday to 'provide medical support...sanitation, surveillance and public health services support to the people of Ambae,' Dr Leodoro said.

'I am confirming that heavy ash fall has caused skin and eye irritations, and exacerbated breathing conditions like asthma,' continued Dr Leodoro.

'We are also working very closely with our disease surveillance teams to monitor reported cases of Mumps, acute gastroenteritis and dengue in all Ambae residents but particularly those at evacuation centres.'

'I am grateful to the Australian government ... for supporting these teams to deploy and provide medical, surgical, mental health, psychosocial support, logistics, water, sanitation, surveillance and public health services support to the people of Ambae,' he said.

Australian has helped Vanuatu support teams by deploying and providing medical, surgical, mental health, psychosocial support, logistics, water, sanitation, surveillance and public health services, Dr Leodoro said