A volcano in southern Japan is blasting out chunks of magma in the first such eruption in 22 years, causing flight cancellations and prompting warnings to stay away from its crater.

The Japan Meteorological Agency said Friday that Mount Aso had spewed out lava debris and smoke, shooting plumes of ash a kilometer (3,280 feet) into the sky. Dozens of flights from Kumamoto, the nearest city, have been canceled.

The observatory does not expect the eruption to increase in scale. Mount Aso, about 1,000 kilometers (625 miles) southwest of Tokyo on Kyushu island, is one of the world's largest. Earthquakes and other seismic activity stepped up in late August.

Eruptions by another volcano, Mount Ontake, in Nagano west of Tokyo killed more than 50 people in late September.