New Zealand's scientists on Tuesday increased the alert level for the volcano below the country's biggest lake, which caused the largest eruption on Earth in the past 5,000 years when it last exploded about 1,800 years ago.

In a statement, geological agency GeoNet said it had detected almost 700 small earthquakes below Lake Taupo, the caldera created by the giant volcano, and had raised the volcanic alert level to 1 from 0.