New Zealand scientists have increased the alert level for a huge volcano - which was the source of the Earth's largest eruption in the past 5,000 years.

Geological agency GeoNet said it had detected almost 700 small earthquakes below Lake Taupo, the caldera created by Taupo Volcano and New Zealand's biggest lake.

It said in a statement that it had raised the volcanic alert level to 1 from 0.

The volcanic alert system is based on six escalating levels of unrest, but Geonet notes that eruptions may occur at any level, and levels may not move in sequence as activity can change rapidly.

The Taupo volcano last exploded around 1,800 years ago, when it spewed more than 100 cubic kilometres of material into the atmosphere around 200 BCE.

The eruption devastated a large area of New Zealand's central North Island in a period before human habitation.

Geonet says the eruption was the largest on the planet in the past 5,000 years.

The agency added this was the first time it had raised the Taupo Volcano alert level to 1, but this was not the first time there had been unrest and said the chance of an eruption remains very low.

Earthquakes 'could continue'

It said: "The earthquakes and deformation could continue for the coming weeks or months."

New Zealand sits on the boundary between the Pacific and Australian tectonic plates and experiences significant volcanism and earthquakes.

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In 2019, White Island, known as Whakaari, suddenly erupted and spewed steam and ash, killing 22 people and seriously injuring 25, mostly tourists.