The country's government estimates that at least 5,000 people have left the villages located near the volcano, which began spewing ash on Wednesday morning, the Radio New Zealand broadcaster reported.
The eruption, which has seen volcanic ash hurled some 10 miles up, already became the strongest of a kind on Bismarck Archipelago in the past century. However, the nearby volcanic observatory in the city of Rabaul said that seismic activity had returned to normal, and Ulawun had calmed down by early Thursday.
Papua New Guinea is part of the so-called Pacific Ring of Fire, a tectonic fault with high seismic activity, which accounts for about 90 percent of all earthquakes on Earth.
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