"If there was a big eruption there could be a disaster, so we have taken the precautionary measure of moving people," John Sese, director general of the prime minister's office, told Reuters from the capital Port Vila.

Sese said an evacuation plan was in place, but no emergency had been declared as volcanic activity remained at level two on a scale of five.

Vanuatu is a string of 83 islands in the southwest Pacific with several active volcanoes. The Aoba volcano, the country's most voluminous, is a 2,500 cubic km basaltic shield volcano.

It rises 3,900 metres (12,800 feet) above sea level and was capped with crater lakes some 360 years ago after erupting. The lake on top of the volcano holds about 50 million cubic metres of water.

The last known eruptions, similar to current levels of activity, occured in 1994 and 1995. In 1914 falling ash from an eruption caused 12 casualties and 120 years ago a large eruption annihilated villages on the southeast of the island, Vanuatu media said.