Reimposing a state of emergency on Ambae, Vanuatu's government insists the volcanic island's entire population must be evacuated.
The volcano at the island's centre, Manaro, has been erupting in phases since last year. But its activity intensified in the past week, causing ash fall so severe that the sun was blocked.
Vanuatu's Meteorological and Geo-Hazards Department raised the threat level to three (the maximum level is five) last weekend.
The director of the department, Esline Garaebiti, said its staff were closely monitoring Manaro, which she said was in its fourth phase of activity since last September.
Each phase has seen an intensification of volcanic activity, with this month's eruption leaving the island blanketed in ash.
"We're seeing very significant impacts on the island at the moment," she explained, adding that after the latest eruption, there was particularly heavy ashfall in Ambae's southern parts.
"Our technical team on site has estimated about 200 millimetres of ash on some parts."
After two earlier evacuation exercises, the Council of Ministers has moved swiftly with a two-month evacuation plan which it describes as compulsory.
One of Ambae's three MPs, Jacob Mata, said some local people will want to stay, and should be allowed to do so.
But the Internal Affairs Minister Andrew Napuat said this time it was different from a previous, voluntary evacuation earlier this year.
"I think that the people might have been thinking that the situation will be stable, will be okay. At this stage it's very clear that the situation will only get worse in the days to come, and so it's important for the people to move out of the island.
"We are, as a government, the council of ministers have already made that decision for them to move. And we will be asking their co-operation to co-operate with us so that we can get them to safety," Mr Napuat said.
Around ten thousand Ambae people were reported to have moved to neighbouring islands of Santo and Maewo after an earlier mass evacuation last year.
Most subsequently returned, although hundreds remain on Santo from the more recent, voluntary evacuation. However considering the latest volcanic activity and closure of services on island, the government wants everyone to leave, and plans to evacuate the bulk of them to Maewo.
But Jacob Mata said that many Ambae people had already moved to Santo or Port Vila, and argued that Maewo lacked the services to cater for people from Ambae
"You're talking about seven, eight, nine thousand people, with only six or seven (thousand) people on Maewo, and no water or electricity," Mr Mata said.
"That's the whole thing about the evacuation to Maewo. There is no health centre, there is nothing there."
Mr Mata said it made more sense for people to move to Vanuatu's largest island of Santo where there are more resources available, and where hundreds of Ambae people had already moved, albeit with mixed results.
But Mr Napuat said the government assessment team had already identified land on Maewo where Ambae communities could best be accommodated.
"It's all related to the provincial administrative concerns, and especially the support that's been given to the province, and also the cultural links that people have, and we want to continue to maintain that. And since the people of Maewo have offered to allow the people of Ambae to go there for the relocation, I think it's a good idea."
In the meantime, Ambae communities were readying to relocate in two evacuation centres, and the government was appealing to shipping operators to give it reasonable rates to help transport the evacuees.
Mr Mata estimated that about six thousand people remained on Ambae, while Mr Napuat felt it was less than ten thousand.
The minister said the government estimated it would cost more than 18 million US dollars (2 billion vatu) to meet the evacuated communities' food, water health, education and accommodation needs.
Mr Napuat said this will require help from Vanuatu's development partners.